传感器外文翻译文献
电容式传感器的外文文献翻译、中英文翻译、外文翻译
参考资料原文：Capacitive sensors and the main features of the basic concepts: The measured volume of the machinery, such as displacement, pressure change is converted to the sensor capacitance. It is the sensitive part of the capacitor with variable parameters. Its most common form is composed of two parallel electrodes, a very inter-air as the medium of the capacitor, if the neglect edge effects, the capacitance for the capacitor plate ε A / δ, where εis a very inter-medium dielectric constant, A two electrode effective area covered by each other, δ is the distance between two electrodes. δ, A, εone of the three parameters will lead to the change in capacitance changes can be used for measurement. Therefore capacitive sensors can be divided into polar distance change type, change type size, media type three types of changes.Most from the changes in small type generally used to measure the linear displacement, or as a result of force, pressure, vibration caused by changes in polar distance (see capacitive pressure sensors). Change type size generally used to measure the angular displacement or linear displacement larger. Changes in media type commonly used in level measurement and a variety of media, temperature, density, humidity measurement. The advantage of the sensor capacitor structure is simple, inexpensive, high sensitivity,过载能力strong, good dynamic response and high temperature, radiation, vibration and other adverse conditions of strong adaptability and strong. The disadvantage is that there are non-linear output, parasitic capacitance and the distributed capacitance on the sensitivity and accuracy the impact of larger and more complex circuits, such as connectivity. Since the late 70s, with the development of integrated circuit technology, a packaging and micro-measuring instrument with capacitive sensors.This new type of distributed capacitance sensors can greatly reduce the impact to overcome the inherent drawbacks. Capacitive sensor is a very wide use, a great potential for development of the sensor.Capacitive sensor working principle：Capacitive sensor surface of the induction of two coaxial metal electrode composition, much like "open" capacitor electrode, the two electrodes form a capacitor, in series with the RC oscillation circuit. Power when connected, RC oscillator is notoscillating, when a goal of moving around electrical capacitor, the capacitor capacity increased, the oscillator to start oscillation. Circuit after the passage of the deal, will be two kinds of vibration and vibration signals into switching signals, which played a detection purpose of the existence of any objects. The sensor can detect metal objects, but also to detect non-metallic objects, metal objects can move away from the largest, non-metallic objects on the decision to move away from the dielectric constant material, the greater the dielectric constant materials, the availability of action the greater distance.Application of capacitive sensors：Capacitive sensor can be used to measure linear displacement, angular displacement, vibration amplitude, especially suitable for measuring high-frequency vibration amplitude, precision rotary axis accuracy, acceleration and other mechanical parameters. Pole-changing type of application from a smaller displacement in the measurement range to several hundred microns in 0.01m, precision can reach 0.01m, a resolution of up to 0.001m. Change type size larger displacement can be measured, for the zero-range a few millimeters to a few hundred mm, 0.5 percent better than the linear resolution of 0.01 ~ 0.001m. Capacitive angular displacement sensor point of view and the dynamic range to a few degrees, a resolution of about 0.1 "up to the stability of the zero angle-second, widely used in precision angle measurement, such as for high-precision gyroscopes and accelerometers tilting . capacitive measurement sensor can measure the peak amplitude for the 0 ~ 50m, a frequency of 10 ~ 2kHz, sensitivity is higher than 0.01m, non-linear error of less than 0.05m.Capacitive sensor can also be used to measure pressure, differential pressure, level, surface, composition content (such as oil, the water content of food), non-metallic coating materials, such as film thickness, dielectric measurements of humidity, density, thickness, etc., in the automatic detection and control systems are also often used as a location signal generator. Capacitive differential pressure sensor measuring range up to 50MPa, an accuracy of ± 0.25% ~ ± 0.5%. Capacitive sensor for measuring range of the thickness of a few hundred microns, resolution of up to 0.01m. Capacitive Proximity Switches can not only detect metal, but also can detect plastic, wood,paper, and other dielectric liquids, but can not achieve the ultra-small, the movement distance of about 10 ~ 20mm. Electrostatic capacitive level switch is widely used in detection is stored in the tank, hopper, such as the location of containers in a variety of objects of a mature product. When the capacitive sensor measuring metal surface conditions, from the size, vibration amplitude is often used very variable from unilateral type, when the measured object is a capacitor electrode, and the other electrode in the sensor inside. This type of sensor is a non-contact measurement, dynamic range is relatively small, about a few millimeters is about the precision of more than 0.1m, a resolution of 0.01 ~ 0.001m.译文：电容式传感器的基本概念及主要特点:把被测的机械量，如位移、压力等转换为电容量变化的传感器。
红外传感器论文中英文资料对照外文翻译
中英文资料对照外文翻译外文资料Moving Object Counting with an Infrared Sensor NetworkBy KI, Chi KeungAbstractWireless Sensor Network (WSN) has become a hot research topic recently. Great benefit can be gained through the deployment of the WSN over a wide range of applications, covering the domains of commercial, military as well as residential. In this project, we design a counting system which tracks people who pass through a detecting zone as well as the corresponding moving directions. Such a system can be deployed in traffic control, resource management, and human flow control. Our design is based on our self-made cost-effective Infrared Sensing Module board which co-operates with a WSN. The design of our system includes Infrared Sensing Module design, sensor clustering, node communication, system architecture and deployment. We conduct a series of experiments to evaluate the system performance which demonstrates the efficiency of our Moving Object Counting system.Keywords:Infrared radiation，Wireless Sensor Node1.1 Introduction to InfraredInfrared radiation is a part of the electromagnetic radiation with a wavelength lying between visible light and radio waves. Infrared have be widely used nowadays including data communications, night vision, object tracking and so on. People commonly use infrared in data communication, since it is easily generated and only suffers little from electromagnetic interference. Take the TV remote control as an example, which can be found in everyone's home. The infrared remote control systems use infrared light-emitting diodes (LEDs) to send out an IR (infrared) signal when the button is pushed. A different pattern of pulses indicates the corresponding button being pushed. To allow the control of multiple appliances such as a TV, VCR, and cable box, without interference, systems generally have a preamble and an address to synchronize the receiver and identify the source and location of the infrared signal. To encode the data, systems generally vary the width of the pulses (pulse-width modulation) or the width of the spaces between the pulses (pulse space modulation). Another popular system, bi-phase encoding, uses signal transitions to convey information. Each pulse is actually a burst of IR at the carrier frequency. A 'high' means a burst of IR energy at the carrier frequency and a 'low' represents an absence of IR energy. There is no encoding standard. However, while a great many home entertainment devices use their own proprietary encoding schemes, somequasi-standards do exist. These include RC-5, RC-6, and REC-80. In addition, many manufacturers, such as NEC, have also established their own standards.Wireless Sensor Network (WSN) has become a hot research topic recently. Great benefit can be gained through the deployment of the WSN over a wide range of applications, covering the domains of commercial, military as well as residential. In this project, we design a counting system which tracks people who pass through a detecting zone as well as the corresponding moving directions. Such a system can be deployed in traffic control, resource management, and human flow control. Our design is based on our self-made cost-effective Infrared Sensing Module board which co-operates with a WSN. The design of our system includes Infrared Sensing Module design, sensor clustering, node communication, system architecture and deployment. We conduct a series of experiments to evaluate the system performance which demonstrates the efficiency of our Moving Object Counting system.1.2 Wireless sensor networkWireless sensor network (WSN) is a wireless network which consists of a vast number of autonomous sensor nodes using sensors to monitor physical or environmental conditions, such as temperature, acoustics, vibration, pressure, motion or pollutants, at different locations. Each node in a sensor network is typically equipped with a wireless communications device, a small microcontroller, one or more sensors, and an energy source, usually a battery. The size of a single sensor node can be as large as a shoebox and can be as small as the size of a grain of dust, depending on different applications. The cost of sensor nodes is similarly variable, ranging from hundreds of dollars to a few cents, depending on the size of the sensor network and the complexity requirement of the individual sensor nodes. The size and cost are constrained by sensor nodes, therefore, have result in corresponding limitations on available inputs such as energy, memory, computational speed and bandwidth. The development of wireless sensor networks (WSN) was originally motivated by military applications such as battlefield surveillance. Due to the advancement in micro-electronic mechanical system technology (MEMS), embedded microprocessors, and wireless networking, the WSN can be benefited in many civilian application areas, including habitat monitoring, healthcare applications, and home automation.1.3 Types of Wireless Sensor NetworksWireless sensor network nodes are typically less complex than general-purpose operating systems both because of the special requirements of sensor network applications and the resource constraints in sensor network hardware platforms. The operating system does not need to include support for user interfaces. Furthermore, the resource constraints in terms of memory and memory mapping hardware support make mechanisms such as virtual memory either unnecessary or impossible to implement. TinyOS [TinyOS] is possibly the first operating system specifically designed for wireless sensor networks. Unlike most other operating systems, TinyOS is based on an event-driven programming model instead of multithreading. TinyOS programs are composed into event handlers and tasks with run to completion-semantics. When an external event occurs, such as an incomingdata packet or a sensor reading, TinyOS calls the appropriate event handler to handle the event. The TinyOS system and programs are both written in a special programming language called nesC [nesC] which is an extension to the C programming language. NesC is designed to detect race conditions between tasks and event handlers. There are also operating systems that allow programming in C. Examples of such operating systems include Contiki [Contiki], and MANTIS. Contiki is designed to support loading modules over the network and supports run-time loading of standard ELF files. The Contiki kernel is event-driven, like TinyOS, but the system supports multithreading on a per-application basis. Unlike the event-driven Contiki kernel, the MANTIS kernel is based on preemptive multithreading. With preemptive multithreading, applications do not need to explicitly yield the microprocessor to other processes.1.4 Introduction to Wireless Sensor NodeA sensor node, also known as a mote, is a node in a wireless sensor network that is capable of performing processing, gathering sensory information and communicating with other connected nodes in the network. Sensor node should be in small size, consuming extremely low energy, autonomous and operate unattended, and adaptive to the environment. As wireless sensor nodes are micro-electronic sensor device, they can only be equipped with a limited power source. The main components of a sensor node include sensors, microcontroller, transceiver, and power source. Sensors are hardware devices that can produce measurable response to a change in a physical condition such as light density and sound density. The continuous analog signal collected by the sensors is digitized by Analog-to-Digital converter. The digitized signal is then passed to controllers for further processing. Most of the theoretical work on WSNs considers Passive and Omni directional sensors. Passive and Omni directional sensors sense the data without actually manipulating the environmen t with active probing, while no notion of “direction” involved in these measurements. Commonly people deploy sensor for detecting heat (e.g. thermal sensor), light (e.g. infrared sensor), ultra sound (e.g. ultrasonic sensor), or electromagnetism (e.g. magnetic sensor). In practice, a sensor node can equip with more than one sensor. Microcontroller performs tasks, processes data and controls the operations of other components in the sensor node. The sensor node is responsible for the signal processing upon the detection of the physical events as needed or on demand. It handles the interruption from the transceiver. In addition, it deals with the internal behavior, such as application-specific computation.The function of both transmitter and receiver are combined into a single device know as transceivers that are used in sensor nodes. Transceivers allow a sensor node to exchange information between the neighboring sensors and the sink node (a central receiver). The operational states of a transceiver are Transmit, Receive, Idle and Sleep. Power is stored either in the batteries or the capacitors. Batteries are the main source of power supply for the sensor nodes. Two types of batteries used are chargeable and non-rechargeable. They are also classified according to electrochemical material used for electrode such as NiCd(nickel-cadmium), NiZn(nickel-zinc), Nimh(nickel metal hydride), and Lithium-Ion. Current sensors are developed which are able to renewtheir energy from solar to vibration energy. Two major power saving policies used are Dynamic Power Management (DPM) and Dynamic V oltage Scaling (DVS). DPM takes care of shutting down parts of sensor node which are not currently used or active. DVS scheme varies the power levels depending on the non-deterministic workload. By varying the voltage along with the frequency, it is possible to obtain quadratic reduction in power consumption.1.5 ChallengesThe major challenges in the design and implementation of the wireless sensor network are mainly the energy limitation, hardware limitation and the area of coverage. Energy is the scarcest resource of WSN nodes, and it determines the lifetime of WSNs. WSNs are meant to be deployed in large numbers in various environments, including remote and hostile regions, with ad-hoc communications as key. For this reason, algorithms and protocols need to be lifetime maximization, robustness and fault tolerance and self-configuration. The challenge in hardware is to produce low cost and tiny sensor nodes. With respect to these objectives, current sensor nodes usually have limited computational capability and memory space. Consequently, the application software and algorithms in WSN should be well-optimized and condensed. In order to maximize the coverage area with a high stability and robustness of each signal node, multi-hop communication with low power consumption is preferred. Furthermore, to deal with the large network size, the designed protocol for a large scale WSN must be distributed.1.6 Research IssuesResearchers are interested in various areas of wireless sensor network, which include the design, implementation, and operation. These include hardware, software and middleware, which means primitives between the software and the hardware. As the WSNs are generally deployed in the resources-constrained environments with battery operated node, the researchers are mainly focus on the issues of energy optimization, coverage areas improvement, errors reduction, sensor network application, data security, sensor node mobility, and data packet routing algorithm among the sensors. In literature, a large group of researchers devoted a great amount of effort in the WSN. They focused in various areas, including physical property, sensor training, security through intelligent node cooperation, medium access, sensor coverage with random and deterministic placement, object locating and tracking, sensor location determination, addressing, energy efficient broadcasting and active scheduling, energy conserved routing, connectivity, data dissemination and gathering, sensor centric quality of routing, topology control and maintenance, etc.中文译文移动目标点数与红外传感器网络作者KI, Chi Keung摘要无线传感器网络(WSN)已成为最近的一个研究热点。
传感器技术论文中英文对照资料外文翻译文献
传感器技术论文中英文对照资料外文翻译文献Development of New Sensor TechnologiesSensors are devices that can convert physical。
chemical。
logical quantities。
etc。
into electrical signals。
The output signals can take different forms。
such as voltage。
current。
frequency。
pulse。
etc。
and can meet the requirements of n n。
processing。
recording。
display。
and control。
They are indispensable components in automatic n systems and automatic control systems。
If computers are compared to brains。
then sensors are like the five senses。
Sensors can correctly sense the measured quantity and convert it into a corresponding output。
playing a decisive role in the quality of the system。
The higher the degree of n。
the higher the requirements for sensors。
In today's n age。
the n industry includes three parts: sensing technology。
n technology。
and computer technology。
热电偶温度传感器中英文对照外文翻译文献
中英文对照外文翻译文献(文档含英文原文和中文翻译)外文翻译：Thermocouple Temperatur sensorIntroduction to ThermocouplesThe thermocouple is one of the simplest of all sensors. It consists of two wires of dissimilar metals joined near the measurement point. The output is a small voltage measured between the two wires.While appealingly simple in concept, the theory behind the thermocouple is subtle, the basics of which need to be understood for the most effective use of the sensor.Thermocouple theoryA thermocouple circuit has at least two junctions: the measurement junction and a reference junction. Typically, the reference junction is created where the two wires connect to the measuring device. This second junction it is really two junctions: one for each of the two wires, but because they are assumed to be at the same temperature (isothermal) they are considered as one (thermal) junction. It is the point where the metals change - from the thermocouple metals to what ever metals are used in the measuring device - typically copper.The output voltage is related to the temperature difference between the measurement and the reference junctions. This is phenomena is known as the Seebeck effect. (See the Thermocouple Calculator to get a feel for the magnitude of the Seebeck voltage). The Seebeck effect generates a small voltage along the length of a wire, and is greatest where the temperature gradient is greatest. If the circuit is of wire of identical material, then they will generate identical but opposite Seebeck voltages which will cancel. However, if the wire metals are different the Seebeck voltages will be different and will not cancel.In practice the Seebeck voltage is made up of two components: the Peltiervoltage generated at the junctions, plus the Thomson voltage generated in the wires by the temperature gradient.The Peltier voltage is proportional to the temperature of each junction while the Thomson voltage is proportional to the square of the temperature difference between the two junctions. It is the Thomson voltage that accounts for most of the observed voltage and non-linearity in thermocouple response.Each thermocouple type has its characteristic Seebeck voltage curve. The curve is dependent on the metals, their purity, their homogeneity and their crystal structure. In the case of alloys, the ratio of constituents and their distribution in the wire is also important. These potential inhomogeneous characteristics of metal are why thick wire thermocouples can be more accurate in high temperature applications, when the thermocouple metals and their impurities become more mobile by diffusion.The practical considerations of thermocouplesThe above theory of thermocouple operation has important practical implications that are well worth understanding:1. A third metal may be introduced into a thermocouple circuit and have no impact, provided that both ends are at the same temperature. This means that the thermocouple measurement junction may be soldered, brazed or welded without affecting the thermocouple's calibration, as long as there is no net temperature gradient along the third metal.Further, if the measuring circuit metal (usually copper) is different to that of the thermocouple, then provided the temperature of the two connecting terminals is the same and known, the reading will not be affected by the presence of copper.2. The thermocouple's output is generated by the temperature gradient along the wires and not at the junctions as is commonly believed. Therefore it is important that the quality of the wire be maintained where temperature gradients exists. Wire quality can be compromised by contamination from its operating environment and the insulating material. For temperatures below 400°C, contamination of insulated wires is generally not a problem. At temperatures above 1000°C, the choice of insulationand sheath materials, as well as the wire thickness, become critical to the calibration stability of the thermocouple.The fact that a thermocouple's output is not generated at the junction should redirect attention to other potential problem areas.3. The voltage generated by a thermocouple is a function of the temperature difference between the measurement and reference junctions. Traditionally the reference junction was held at 0°C by an ice bath:The ice bath is now considered impractical and is replace by a reference junction compensation arrangement. This can be accomplished by measuring the reference junction temperature with an alternate temperature sensor (typically an RTD or thermistor) and applying a correcting voltage to the measured thermocouple voltage before scaling to temperature.The correction can be done electrically in hardware or mathematically in software. The software method is preferred as it is universal to all thermocouple types (provided the characteristics are known) and it allows for the correction of the small non-linearity over the reference temperature range.4. The low-level output from thermocouples (typically 50mV full scale) requires that care be taken to avoid electrical interference from motors, power cable, transformers and radio signal pickup. Twisting the thermocouple wire pair (say 1 twist per 10 cm) can greatly reduce magnetic field pickup. Using shielded cable or running wires in metal conduit can reduce electric field pickup. The measuring device should provide signal filtering, either in hardware or by software, with strong rejection of the line frequency (50/60 Hz) and its harmonics.5. The operating environment of the thermocouple needs to be considered. Exposure to oxidizing or reducing atmospheres at high temperature can significantly degrade some thermocouples. Thermocouples containing rhodium (B,R and S types) are not suitable under neutron radiation.The advantages and disadvantages of thermocouplesBecause of their physical characteristics, thermocouples are the preferred methodof temperature measurement in many applications. They can be very rugged, are immune to shock and vibration, are useful over a wide temperature range, are simple to manufactured, require no excitation power, there is no self heating and they can be made very small. No other temperature sensor provides this degree of versatility.Thermocouples are wonderful sensors to experiment with because of their robustness, wide temperature range and unique properties.On the down side, the thermocouple produces a relative low output signal that is non-linear. These characteristics require a sensitive and stable measuring device that is able provide reference junction compensation and linearization.Also the low signal level demands that a higher level of care be taken when installing to minimise potential noise sources.The measuring hardware requires good noise rejection capability. Ground loops can be a problem with non-isolated systems, unless the common mode range and rejection is adequate.Types of thermocoupleAbout 13 'standard' thermocouple types are commonly used. Eight have been given an internationally recognised letter type designators. The letter type designator refers to the emf table, not the composition of the metals - so any thermocouple that matches the emf table within the defined tolerances may receive that table's letter designator.Some of the non-recognised thermocouples may excel in particular niche applications and have gained a degree of acceptance for this reason, as well as due to effective marketing by the alloy manufacturer. Some of these have been given letter type designators by their manufacturers that have been partially accepted by industry.Each thermocouple type has characteristics that can be matched to applications. Industry generally prefers K and N types because of their suitability to high temperatures, while others often prefer the T type due to its sensitivity, low cost and ease of use.A table of standard thermocouple types is presented below. The table also showsthe temperature range for extension grade wire in brackets.Accuracy of thermocouplesThermocouples will function over a wide temperature range - from near absolute zero to their melting point, however they are normally only characterized over their stable range. Thermocouple accuracy is a difficult subject due to a range of factors. In principal and in practice a thermocouple can achieve excellent results (that is, significantly better than the above table indicates) if calibrated, used well below its nominal upper temperature limit and if protected from harsh atmospheres. At higher temperatures it is often better to use a heavier gauge of wire in order to maintain stability (Wire Gauge below).As mentioned previously, the temperature and voltage scales were redefined in 1990. The eight main thermocouple types - B, E, J, K, N, R, S and T - were re-characterised in 1993 to reflect the scale changes. (See: NIST Monograph 175 for details). The remaining types: C, D, G, L, M, P and U appear to have been informally re-characterised.Try the thermocouple calculator. It allows you the determine the temperature by knowing the measured voltage and the reference junction temperature.Thermocouple wire gradesThere are different grades of thermocouple wire. The principal divisions are between measurement grades and extension grades. The measurement grade has the highest purity and should be used where the temperature gradient is significant. The standard measurement grade (Class 2) is most commonly used. Special measurement grades (Class 1) are available with accuracy about twice the standard measurement grades.The extension thermocouple wire grades are designed for connecting the thermocouple to the measuring device. The extension wire may be of different metals to the measurement grade, but are chosen to have a matching response over a much reduced temperature range - typically -40°C to 120°C. The reason for using extension wire is reduced cost - they can be 20% to 30% of the cost of equivalent measurementgrades. Further cost savings are possible by using thinnergauge extension wire and a lower temperature rated insulation.Note: When temperatures within the extension wire's rating are being measured, it is OK to use the extension wire for the entire circuit. This is frequently done with T type extension wire, which is accurate over the -60 to 100°C range.Thermocouple wire gaugeAt high temperatures, thermocouple wire can under go irreversible changes in the form of modified crystal structure, selective migration of alloy components and chemical changes originating from the surface metal reacting to the surrounding environment. With some types, mechanical stress and cycling can also induce changes.Increasing the diameter of the wire where it is exposed to the high temperatures can reduce the impact of these effects.The following table can be used as a very approximate guide to wire gauge:At these higher temperatures, the thermocouple wire should be protected as much as possible from hostile gases. Reducing or oxidizing gases can corrode some thermocouple wire very quickly. Remember, the purity of the thermocouple wire is most important where the temperature gradients are greatest. It is with this part of the thermocouple wiring where the most care must be taken.Other sources of wire contamination include the mineral packing material and the protective metal sheath. Metallic vapour diffusion can be significant problem at high temperatures. Platinum wires should only be used inside a nonmetallic sheath, such as high-purity alumna.Neutron radiation (as in a nuclear reactor) can have significant permanent impact on the thermocouple calibration. This is due to the transformation of metals to different elements.High temperature measurement is very difficult in some situations. In preference, use non-contact methods. However this is not always possible, as the site of temperature measurement is not always visible to these types of sensors.Colour coding of thermocouple wireThe colour coding of thermocouple wire is something of a nightmare! There are at least seven different standards. There are some inconsistencies between standards, which seem to have been designed to confuse. For example the colour red in the USA standard is always used for the negative lead, while in German and Japanese standards it is always the positive lead. The British, French and International standards avoid the use of red entirely!Thermocouple mountingThere are four common ways in which thermocouples are mounted with in a stainless steel or Inconel sheath and electrically insulated with mineral oxides. Each of the methods has its advantages and disadvantages.Sealed and Isolated from Sheath: Good relatively trouble-free arrangement. The principal reason for not using this arrangement for all applications is its sluggish response time - the typical time constant is 75 secondsSealed and Grounded to Sheath: Can cause ground loops and other noise injection, but provides a reasonable time constant (40 seconds) and a sealed enclosure.Exposed Bead: Faster response time constant (typically 15 seconds), but lacks mechanical and chemical protection, and electrical isolation from material being measured. The porous insulating mineral oxides must be sealedExposed Fast Response: Fastest response time constant, typically 2 seconds but with fine gauge of junction wire the time constant can be 10-100 ms. In addition to problems of the exposed bead type, the protruding and light construction makes the thermocouple more prone to physical damage.Thermocouple compensation and linearizationAs mentioned above, it is possible to provide reference junction compensation in hardware or in software. The principal is the same in both cases: adding a correction voltage to the thermocouple output voltage, proportional to the reference junction temperature. To this end, the connection point of the thermocouple wires to the measuring device (i.e. where the thermocouple materials change to the copper of thecircuit electronics) must be monitored by a sensor. This area must be design to be isothermal, so that the sensor accurately tracks both reference junction temperatures.The hardware solution is simple but not always as easy to implement as one might expect.The circuit needs to be designed for a specific thermocouple type and hence lacks the flexibility of the software approach.The software compensation technique simplifies the hardware requirement, by eliminating the reference sensor amplifier and summing circuit (although a multiplexer may be required).The software algorithm to process the signals needs to be carefully written. A sample algorithm details the process.A good resource for thermocouple emf tables and coefficients is at the US Commerce Dept's NIST web site. It covers the B, E, J, K, N, R, S and T types.The thermocouple as a heat pumpThe thermocouple can function in reverse. If a current is passed through a thermocouple circuit, one junction will cool and the other warm. This is known as the Peltier Effect and is used in small cooling systems. The effect can be demonstrated by alternately passing a current through a thermocouple circuit and then quickly measuring the circuit's Seebeck voltage. This process has been used, with very fine thermocouple wire (0.025 mm with about a 10 mA current), to measure humidity by ensuring the cooled junction drops below the air's dew point. This causes condensation to form on the cooled junction. The junction is allowed to return to ambient, with the temperature curve showing an inflection at the dew point caused by the latent heat of vaporization.Measuring temperature differencesThermocouples are excellent for measuring temperatures differences, such as the wet bulb depression in measuring humidity. Sensitivity can be enhanced by constructing a thermopile - a number of thermocouple circuits in series.In the above example, the thermopile output is proportional to the temperaturedifference T1 - T2, with a sensitivity three times that of a single junction pair. In practice, thermopiles with two to hundreds of junctions are used in radiometers, heat flux sensors, flow sensors and humidity sensors. The thermocouple materials can be in wire form, but also printed or etched as foils and even electroplated.An excellent example of the thermopile is in the heat flux sensors manufactured by Hukseflux Thermal Sensors. Also see RdF Corp. and Exergen Corp.The thermocouple is unique in its ability to directly measure a temperature difference. Other sensor types require a pair of closely matched sensors to ensure tracking over the entire operational temperature range.The thermoelectric generatorWhile the Seebeck voltage is very small (in the order of 10-70μV/°C), if the circuit's electrical resistance is low (thick, short wires), then large currents are possible (e.g. many amperes). An efficiency trade-off of electrical resistance (as small as possible) and thermal resistance (as large as possible) between the junctions is the major issue. Generally, electrical and thermal resistances trend together with different materials. The output voltage can be increased by wiring as a thermopile.The thermoelectric generator has found its best-known application as the power source in some spacecraft. A radioactive material, such as plutonium, generates heat and cooling is provided by heat radiation into space. Such an atomic power source can reliably provide many tens of watts of power for years. The fact that atomic generators are highly radioactive prevents their wider application.译文：热电偶温度传感器热电偶的定义热电偶是最简单的传感器之一。
湿度传感器系统中英文对照外文翻译文献
中英文资料外文翻译文献英文:The right design for a relative humidity sensor systemOptimizing the response characteristics and accuracy of a humidity sensor system1 OverviewTo make the right choice when selecting a relative humidity sensor for an application, it is important to know and to be able to judge the deciding factors. In addition to long-term stability, which is a measure on how much a sensor changes its properties over time, these factors also include the measurement accuracy and the response characteristics of the sensor. Capacitive humidity sensors are based on the principle that a humidity-sensitive polymer absorbs or releases moisture as a function of the relative ambient humidity. Because this method is only a spot measurement at the sensor location, and usually the humidity of the surroundings is the desired quantity, the sensor must be brought into moisture equilibrium with the surroundings to obtain a precise measurement value. This process is realized by various transport phenomena (cf. the section titled "The housing effect on the response time"), which exhibit a time constant. Accuracy and response time are thus closely dependent on each other, and the design of a humidity measurement system becomes a challenge.2Measurement accuracyThe term measurement accuracy of a humidity sensor is understood primarily to refer to the deviation of the value measured by the sensor from the actual humidity. To determine the measurement accuracy, references, such as chilled mirror hygrometers, whose own tolerance must be taken into account, are used. In addition to this trivial component, humidity sensors require a given time for reaching stable humidity and temperature equilibrium (the humidity is a function of temperature and decreases with increasing temperature; a difference between sensor and ambient temperature leads to measurement errors). This response time thus has a significant effect on the value measured by the sensor and thus on the determinedaccuracy.This time-dependent characteristic is explained in more detail in the following.3Response characteristics and response timeThe response characteristics are defined by various parameters. These are:●The actual response characteristics of the humidity sensor at constant temperature.(1) How quickly the sensitive polymer absorbs or releases moisture until equilibrium is reached (intrinsic response time)(2) How fast the entire system reaches humidity equilibrium (housing effect)●The thermal response characteristics of the humidity sensor at a non-constant temperature(3) The thermal mass of the sensor(4) The system's thermal mass, which is thermally coupled to the sensor (e.g. printed circuit board)(5) Heat sources in the direct surroundings of the sensor (electronic components)(1) and (3) are determined entirely by the sensor itself, (1) primarily by the characteristics of the sensitive polymer.(2) and (4) are primarily determined by the construction of the entire system (shape and size of housing andreadout circuitry).(5) is determined by heat-emitting electronic components.These points will be discussed in more detail in the following.The intrinsic response time (1)Qualitatively, the response characteristics of capacitive humidity sensors look like the following (Fig. 1).Fig. 1: Typical and idealized response characteristics of capacitive humidity sensors (schematic)Because these response characteristics are especially pronounced at high humidity values, an isothermal humidity jump from 40% to 100% was selected here for illustration. The desired ideal behavior of the sensor is indicated in blue. In practice, however, the sensor behaves according to the red line, approximately according to:RH-t=(E-S)*(1-e)+S（t）Here, the time span 1 is usually very short (typ. 1 – 30 min.), in contrast, the time span 2 is very long (typ. Many hours to days). Here the connection of measurement accuracy and response characteristics becomes clear (t until RH=100% is reached). The value at t4 (Fig. 1) is considered to be an exact measured value. However, this assumes that both the humidity and also the temperature remain stable during this entire time, and that the testing waits until this very long measurement time is completed. These conditions are both very hard to achieve and unusual in practice. For the calibration, there are the following two approaches, which both find use in practice (cf. Fig. 2):1.The measured value at t2 (Fig. 1) is used as a calibration reference.Advantage:●The required measurement time for reaching the end value (in the example 100%) isclearly shortened,corresponds to practice, and achieves an apparent short responsetime of the sensor (cf. Fig. 2).Disadvantage:●If the conditions are similar for a long time (e.g., wet periods in outdoor operation),the sensors exceed the correct end value (in the example 100%) undesirably by upto 10% (cf. Fig. 2).2. The measured value at t4 (Fig. 1) is used as a calibration reference.Advantage:●Even for similar conditions over a long time (e.g., wet periods in outdoor operation),an exact measurement result is obtained (cf. Fig. 2).Disadvantage:●For a humidity jump like in Fig. 1, the sensors very quickly deliver the measuredvalue at t2, but reaching a stable end value (about 3-6% higher) takes a long time(apparent longer response time)(cf. Fig. 2).In order to take into account both approaches optimally, the measured values at t3 (cf. Fig. 1) are used as the calibration reference by Sensirion AG.Fig. 2: Response characteristics of different humidity measurement systemsThe housing effect on the response time (2)Here, two types of transport phenomena play a deciding role:●Convection: For this very fast process, the air, whose humidity is to be determined,is transported to the sensor by means of ventilation.●Diffusion: This very slow process is determined by the thermal, molecularself-motion of the water molecules. It occurs even in "stationary" air (e.g., within ahousing), but leads to a long response time.In order to achieve favorable response characteristics in the humidity measurement system, the very fast convection process must be supported by large housing openings and the slow diffusion process must be supported by a small housing around the sensor (small "deadvolume") with "stationary" air reduced to a minimum. The following applies:Thermal effects (3), (4), and (5)Because the total thermal mass of the humidity measurement system (sensor + housing)has a significant effect on its response time, the total thermal mass must be kept as low aspossible. The greater the total thermal mass, the more inert the measurement system becomesthermally and its response time, which is temperature-dependent, increases. In order toprevent measurement errors, the sensor should not be mounted in the vicinity of heatgenerating components.4Summary –what should be taken into account when designing a humidity measurement systemIn order to achieve error-free operation of a humidity-measurement system with response times as short as possible, the following points should be taken into account especially for the selection of the sensor and for the design of the system.●The selection of the humidity sensor element. It should●be as small as possible,●have a thermal mass that is as low as possible,●work with a polymer, which exhibits minimal fluctuations in measured values duringthe time span 2(cf. Fig. 1); testing gives simple information on this condition,●provide calibration, which corresponds to the requirements (see above), e. g.,SHT11/SHT15 from Sensirion.●The housing design (cf. Formula 1). It should●have air openings that are as large as possible in the vicinity of the sensor or thesensor should be operated outside of the housing à good convection!●enclose a "dead volume" that is as small as possible around the sensor àlittlediffusion!●The sensor should be decoupled thermally as much as possible from other components,so that the response characteristics of the sensor are not negatively affected by the thermal inertia of the entire system.(e.g., its own printed circuit board for the humidity sensor, structurally partitioning the housing to create a small volume for the humidity sensor, see Fig. 3)Fig. 3: Mounting example for Sensirion sensors SHT11 and SHT15 with slits for thermal decoupling●The sensor should not be mounted in the vicinity of heat sources. If it was, measuredtemperature would increase and measured humidity decrease.5Design proposalThe challenge is to realize a system that operates cleanly by optimally taking into account all of the points in section 4. The already calibrated SMD humidity sensors SHT11 and SHT15 from Sensirion are the ideal solution. For optimum integration of the sensors in a measurement system, Sensirion AG has also developed a filter cap as an adapter aid, which takes into account as much as possible the points in section 4 and also protects the sensor against contaminants with a filter membrane. Fig. 4 shows schematically how the sensors can be ideally integrated into a housing wall by means of the filter cap SF1.Fig. 4: Filter cap for SHT11 and SHT15In addition to the advantages mentioned above, there is also the option of building an IP67-compatible humidity measurement device (with O-ring, cf. Fig. 4) with optimal performance. Detailed information is available on the Sensirion Web site.译文：相对湿度传感器系统的正确设计湿度传感器系统精度及响应特性的优化1.综述为了在相对湿度的应用方面对传感器做出正确的选择，了解和评估那些起决定作用的因素是非常重要的。
传感器外文文献
Photoelectric sensorKey word:photoeletric effect photoelectric element photoeletric sensor classification sensor application characteristics. Abstract:in the development of science and technology in the modern society,mankind has into rapidly changing information era,people in daily life,the production process,rely mainly on the detection of information technology by acquiring,screening and transmission,to achieve the brake control,automation adjustment,at present our country has put detection techniques listed in one of the priority to the development of science and technology.Because ofmicroelectronics technology,photoelectric semiconductor technology,optical fiber technology and grating technical development makes the application of the photoelectric sensor is growing .The sensor has simple structure, non-contact,high reliability,high precision,measurable parameters and quick response and more simple structure,form etc,and flexible in automatic detection technology,it has been widely applied in photoelectric effect as the theoretical basis,the device by photoelectric material composition.Text:First,theoretical foundation-photoelectric effect Photoelectric effect generally have the photoelectric effect ,optical effect,light born volts effect.The light shines in photoelectric material,according to the electronic absorption material surface energy,if absorbed energy large enough electronic will overcome bound from material and enter the outside space,which changes photoelectron materials ,this king of phenomenon become the conductivity of the photoelectric effect.According to Einstein’s photoelectron effect,photon is moving particles,each photon energy for hv(v for light frequency,h for Planck’s constant,h=6.63*10-34J/HZ),thus different frequency of photons have different energy,light,the higher the frequency,the photon energy is bigger.Assuming all the energy photons to photons,electronic energy will increase,increased energy part of the fetter,positive ions used to overcome another part of converted into electronic energy.According to the law of conservation of energy:1／2mv =hv-A2Type,m for electronic quality,v for electronic escaping the velocity,A microelectronics the work done.From the type that will make the optoelectronic cathode surface escape the necessary conditions are h>A.Due to the different materials have different escaping,so reactive to each kind ofcathode material,incident light has a certain frequency is restricted,when the frequency of incident light under this frequency limit,no matter how the light intensity,won’t produce photoelectron lauch,this frequency limit called“red limit”.The corresponding wavelength for type,c for the speed of light,A reactive for escaping.When is the sun,its electronic energy,absorb the resistivity reduce conductive phenomenon called optical effects.It belongs to the photoelectric effect within.When light is,if in semiconducter electronic energy big with semiconductor of forbidden band width,the electronic energy from the valence band jump into the conduction band,form,and at the same time,the valence band electronic left the corresponding cavities. Electronics,cavitation remained in semiconducter,and participate in electric conductive outside formed under the current role.In addition to metal outer,most insulators and semiconducter have photoelectric effect,particularly remarkable,semiconductor optical effect according to the optoelectronics manufacturing incident light inherent frequency,when light resistance in light,its conductivity increases,resistance drops.The light intensity is strong,its value,if the smaller,its resistance to stop light back to the original value.Semiconductor producted by light illuminate the phenomenon is called light emf,born volts effect on the effect of photoelectric devices have made si-based ones,photoelectric diode,control thyristor and optical couplers,etc.Second,optoelectronic components and characteristics According to the outside optoelectronics manufacturing optoelectronic devices have photoelectron,inflatable phototubes and photoelectric times once tube.1.Phototubes phototubes are various and typical products arevacuum phototubes and inflatable phototubes,light its appearance and structure as shown in figure 1 shows,made of cylindrical metal half cathodic K and is located in the wires cathodic axis of anode in A package of smoke into the vacuum,when incident light within glass shell in the cathode,illuminate A single photon took all of its energy transfer to the cathode materials A free electrons,so as to make the freedom electronic energy increase h.When electrons gain energy more than escape of cathode materials,it reactive A metal surface constraints can overcome escape,form electron emission.This kind of electronic called optoelectronics,optoelectronic escaping the metal surface for after initial kinetic energyPhototubes normal work,anode potential than the cathode, show in figure 2.In one shot more than “red light frequency is premise,escape from the optoelectronic cathode surface by positive potential attracted the anode in photoelectric tube forming space,called the current stream.Then if light intensity increases,the number of photons bombarded the cathode multiplied,unit of time to launch photoelectron number are also increasing,photo-current greatens.In figure 2 shows circuit,current so as to achieve a photoelectric conversion.When the LTT optoelectronic cathode K, electronic escape from the cathode surface,and was the photoelectric anode is an electric current,power plants absorb deoxidization device in the load resistance-I,the voltage. Phototubes photoelectric characteristics fig.03 shows,from the graph in flux knowable,not too big,photoelectric basis characteristics is a straight line.2.Photoelectric times had the sensitivity of vacuum tube duo tolow,so with people developed has magnified the photomultiplier tubes photo-current ability.Figure 4 isphotomultiplier tube structure schematic drawing.From the graph can see photomultiplier tubes also have A cathode K and an anode A,and phototubes different is in its between anode and cathode set up several secondary emission electrodes,D1,D2 and D3…Usually,double electrode for 10~15 levels.Photomultiplier tubes work between adjacent electrode,keeping a certain minimum,including the cathode potential potentials,each multiply electrode potential filtering increases, the anode potential supreme.When the incident light irradiation, cathodic K escape from the optoelectronic cathode multiplied by first accelerated,by high speed electrode D1 bombarded caused secondary electron emission,D1,an incident can generate multiple secondary electron photonics,D1 emit of secondary electron was D1,D2 asked electric field acceleration,converged on D2 and again produce secondary electron emission…So gradually produce secondary electron emission,make electronic increased rapidly,these electronic finally arrived at the anode, form a large anode current.If an level,multiply electrodes at alllevels for sigma,the multiplication of rate is the multiplication of photomultiplier tubes can be considered sigma n rate,therefore,photomultiplier tube has high sensitivity.In the output current is less than 1mA circumstances,it in a very wide photoelectric properties within the scope of the linear relationship with good.Photomultiplier tubes this characteristic, Make it more for light measurement.3.and photoconductive resistance photoconductive resistance within the working principle is based on the photoelectric effect. In semiconducter photosensitive material ends of mount electrode lead,it contains transparent window sealed in the tube and shell element photoconductive resistance.Photoconductive resistance properties and parameters are:1)dark resistance photoconductive resistance at roomtemperature,total dark conditions stable resistance called dark resistance,at the current flow resistance is called dark current.2)Light resistance photoconductive resistance at roomtemperature and certain lighting conditions stable resistance measured,right now is called light resistance of current flow resistance is called light current.4.V olt-ampere characteristics of both ends photoconductive resistance added voltage and current flows throughphotoconductive resistance of the relationship between called volt-ampere characteristics shown,as shown in figure 5.From the graph,the approximate linear volt-ampere characteristics that use should be limited,but when the voltage ends photoconductive resistance,lest than shown dotted lines of power consumption area.光敏电阻的伏安特性5.photoelectric characteristics photoconductive resistance between the poles,light when voltage fixed the relationship between with bright current photoelectric characteristics.Called photoconductive resistance photoelectric characteristics is nonlinear,this is one of the major drawback of photoconductive resistance.6.Spectral characteristics is not the same incident wavelength the sensitivity of photoconductive resistance is different also.Incidence wavelength and photodetector the relationship between relative sensitivity called spectral characteristics.When used according to the wavlength range by metering,choosedifferent material photoconductive resistance.7.Response time by photoconductive resistance after photo-current need light,over a period of time (time) rise to reach its steady value.Similarly,in stop light photo-current also need,over a period of time (down time) to restore the its dark current,this is photoconductive resistance delay characteristic . Photoconductive resistance rise response time and falling response time about 10-1~10-3s,namely the frequency response is 10Hz~1000Hz,visible photoconductive resistance cannot be used in demand quick response occasion,this is one of the main photoconductive resistance shortcoming.8、and temperature characteristic photoconductive resistance by temperature affects greatly,temperature rise,dark current increase,reduced sensitivity,which is another photoconductive resistance shortcoming.9、frequency characteristic frequency characteristics refers to an external voltage and incident light,strong must be photo-current I and incident light,modulation frequency,the relationship between the f,photoelectric diode is the freqency characteristic of the ptotoelectric triode frequency characteristics,this is because of the photoelectric triode shot “yankees there capacitance and carrier base-combed need time’s sake.By usingthe principle of the photoelectric effciency of optoelectronics manufacturing frequency characteristic of the worst,this is due to capture charge carriers and release charge need a certain time’s sake.Three,photoelectric sensorsPhotoelectric sensor is through the light intensity changes into electrical signal changes to achieve control,its basic structure,it first figure 6 by measuring the change of converting the light signal,and then using photoelectric element further will light signals into electrical signal by photoelectric sensor general. Illuminant,optical path and optoelectronics.Three components of photoelectric detection method has high precision,fast response,non-contact wait for an advantage,but measurable parameters of simple structure,sensors,form flexible,threefore, photoelectric sensor in the test and control is widely used.By photoelectric sensor generally is composed of three parts, they are divided into:transmitter and receiver and detection circuit shown,as shown in figure 7,transmitter aimed at the target launch beam,the launch of the beam from semiconductor illuminant,general light emitting diode(LED),laser diode and infrared emission diode.Beam uninterrupted lauch,or change the pulse width. Receivers have photoelectric diode,photoelectrictriode,composed si-based ones.In front of the receiver, equipped with optical components such as lens and aperture,etc.In its back is detection circuit,it can filter out effective signal and the application of the signal.In addition,the structural components in photoelectric switch and launch plate and optical fiber,triangle reflex plate is solid structure launch device.It consists of small triangle cone of reflective materials,can make a beam accurately reflected back from plate,with practical significance.It can be in with the scope of optical axis 0 to 25,make beams change launch Angle from a root almost after launch line,passes reflection or from the rotating polygon.some basic returns.Photoelectric sensor is a kind of depend on is analyte andoptoelectronics and light source,to achieve the relationship between the measured purpose,so the light source photoelectric sensor plays a very important role,photoelectric sensor power if a constant source,power is very important for design,the stability of power directly affect the accuracy of measurement,comonly used illuminant have the following kinds:1,leds is a change electric energy into light energy semiconductor devices.It has small volume,low power consumption,long life,fast response,the advantages of high mechanical strength,and can match and integrated circuits. Therefore,widely used in computer,instruments and automatic control equipment.2,Silk light bulb that is one of the most commomly used illuminant,it has rich infrare light.If chosen optoelectronics, constitutes of infrared sensor sensitive colour filter can be added to the visible tungsten lamps,but only filter with its infrared does illuminant,such,which can effectively prevent other light interference.3,compared with ordinary light laser with energy concentration, directional good,frequency pure,coherence as well as good,is very ideal light sources.The light source,optical path and photoelectric device composition photoelectric sensor used inphotoelectric detection,still must be equipped with appropriate measurement circuit.The photoelectric effect to the measurement circuit of photoelectric element of widerange caused changes needed to convert the voltage or current. Different photoelectric element,the measurement circuit required is not identical also.Several semiconductor introduces below optoelectronic devices commonly used measurement circuit.Figure 9(a)with temperature compensation given the photosensitive diode bridge type measuring circuit.When the incident light intensity slow change,the reverse resistance photosensitive diode is the slow change,the change of the temperature will cause the bridge output voltage,must compensate.Drift picture a photosensitive diode as the test components,another into windows,in neighboring bridge,the change of the temperature in the arms of the influence of two photosensitive diode,therefore,can eliminate the same output with tempereture bridge road drift.Light activated triode incident light in work under low illumination,or hope to get bigger output power,also can match with amplifying circuit,as shown in figure 9 shows.Because even in the glare photosensitive batteries,maximum output voltage also only 0.6V,still cannot make the next level 1 transistor have larger current output,so must add positive bias,as shown in figure 9(a)below.In order to reduce the transistor circuit impedance variations,base si-based ones to reduce as much as possible without light,when the reverse bias inherit in parallel a resistor si-based ones at both ends.Or like figure 9(b)as shown by the positive ge diode produces pressure drop and test the voltage produced when exposed to light,make silicon tube e stack,b the voltage between actuators than 0.7V,and conduction work.This kind of circumstance also can use silicon light batteries,as shown in figure 10(c)below.Semiconductor photoelectric element of photoelectric circuit can also use integrated operational amplifier.Silicon photosensitive diode can be obtained by integrating op-amp large output amplitude,as shown in figure 11(a)below.When light is produced,the optical output voltage in order to guarantee photosensitive diode is reverse biased,in its positive to add a load voltage.Figure 11.(b) give the photocell transform circuit,because the photoelectric si-based ones short-circuit current and illumination of a linear relationship between,so will it up in the op-amp is,inverse-phase input,using these two potential difference between the characteristics of close to zero,can get better effect.In the picture shows conditions,the output voltage U0=2IφR FThe photoelectric element by flux the role of different made from the principle of optical measurement and control system is varied,press the photoelectric element (optical measurement andcontrol system)output nature,namely,can be divided into second analog photoelectric sensor and pulse (switch)photoelectric sensor.Analog photoelectric sensors will be converted into continuous variation of the measure,it is measuered optical with a single value relations between analog photoelectric sensor. According to be measured (objects)method detection of target can be divided into transmission (absorption)type,diffuse type, shading type(beam resistance gears)three categories.So-called transmission style means the object to be tested in optical path in constant light source,the light energy through things,part of being measured by absorption,transmitted light onto photoelectric element,such as measured liquid,gas transparency and photoelectric BiSeJi etc;speed.gratifying the so-called diffuse style means the constant light by the light onto the analyte from the object to be tested,and projected onto surfaces reflect on after optoelectronic devices,such as photoelectric colorrimetric thermometer and light gauge etc;The so-called shading style means the when illuminant issued by the flux of light analyte covered by a part Jing optoelectronics,make projection on the flux change,change the object to be tested and extent of the position with the light path,such as vibration measurement,the size measurement;And in pulse photoelectricsensor in the sensors,photoelectric element in switch work of the state,the current output it is usually only two steady state of the signal,the pulse form used for photoelectric counting and photoelectric speed measurement and so on.And infrared photoelectric sensor classification and working way generally have the following kinds:1,groove photoelectric sensor put a light emitter and a receiver in a slot face-to-face outfit are on opposite sides of the photoelectric groove.Lighter emits infrared light or visible light, and in unimpeded cases light receptors can receive light.But when tested objects from slot zhongtong obsolete , light occluded ,photoelectric switches and action.Output a switch control signal,cut off or connect load current,thus completing a control movement.Groove switch is the overall of detection distance because general structure limits only a few centimeters. 2,DuiShe type optoelectronic sensor if you put lighter and receive light is separated,can make the detection distance increase.By a lighter and an inbox light sensor into a photoelectric switch is called DuiShe separate photoelectric switches,referred to DuiShe photoelectric switch.Its detection distance can reach a few meters and even a dozen meters.When using light-emitting device and recive light device are installedin test object through the path of the sides,test object by blocking light path,accept light implement action output a switch control signals.3,Reflex plate.it photoelectric switch light-emitting device type and receive light device into the same device inside,in its front pack a reflex plate.the using the reflection principle of complete photoelectric control function is called reflex plate.it reflex (or reflector reflx)photoelectric switch.Under normal circumstances, lighter the light reflected by reflex plate.it is received by accept light;Once the light path be test object to block,accept light,the light is not received photoelectric switch is action,output a switch control signals.4,Diffusion reflective photoelectric switches its detection head with a lighter and also an inbox light ware,but no reflex plate.it ahead.Normally lighter for the light collect light is not found. When test object by blocking the light,and the light reflected light,receive part implement received light signals,output a switch signals.Four,I’m the idea of photoelectric sensorWith the development of science and technology people on measuring accuracy had the higher request,this has prompted the pace with the times photoelectric sensor have updated,improvethe main means photoelectric sensor performance is the application of new materials,new technology manufacturing performance is more superior photoelectric element.For example,today the prototype of the photoelectric sensor is a small metal cylindrical equipment,with a calibration lens,transmitter into receiver focused light,the receiver out of cable to the device got to a vacuum tube amplifiers in metal cylinder on the incandescent light bulb inside a small as the light source a strong incandescent lamp sensor.Due to the sensor various defects existing in the fields,gradually faded.To appear, because of it of fiber of excellent performance,then appeared with sensors supporting the use of optical passive components, another fiber without any interference of electromagnetic signal, and can make the sensor of the electronic components and other electrical disturbance in isolation.Have a piece of plastic optical fiber core or plass light core,light outside a metallic core skins and bread this layer metal cortical density lower than light core, so low,the beam refraction in the two materials according to the border(incident Angle within a certain range,reflected),is all. Based on optical principle,all beams can be made by optical fiber to transmission.Two incident beam Angle in an Angle (along the fiber length direction within)by multiple reflectionsfrom the other end after injection,another incident angles than accept the incident light in metal skin,loss.This accept Angle within the biggest incident Angle than two times,this is because fiber slightly larger from air into density larger fiber materials hitting may have a slight refraction.In light of the optical fiber transmission from inside the influence of fiber bending(whether more than bending radius minimal bending radius).Most optical fiber is flexible,easy to install in the narrow space. Photoelectric sensor is a kind of non-contact measurement small electronic measurement equipment,rely on detect its receives the light intensity change,to achieve measurement purposes,and it’s also a vulnerable to external disturbance and lose the measurement accuracy of the device.When be being designed so besides the choice optoelectronic components,still must set GSCC signal and temperature compensating measures used to weaken or eliminate the impact of these factors.。
无线微传感器中英文对照外文翻译文献
无线微传感器中英文对照外文翻译文献(文档含英文原文和中文翻译)A Simple Energy Model for Wireless Microsensor TransceiversAbstract—This paper describes the modelling of shortrange transceivers for microsensor applications. A simple energy model is derived and used to analyze the transceiver battery life. This model takes into account energy dissipation during the start-up, receive, and transmit modes. It shows that there is a significant fixed cost in the transceiver energy consumption and this fixed cost can be driven down by increasing the data rate of the transceiver.I. IntroductionWireless microsensor networks can provide short-range connectivity with significant fault tolerances. These systems find usage in diverse areas such as environmental monitoring, industrial process automation, and field surveillance. As an example, Table I shows a detailed specification for a sensor system used in a factory machine monitoring environment.The major characteristics of a microsensor system are high sensor density, short range transmissions, and low data rate. Depending on the application, there can also be stringent BER and latency requirements. Due to the large density and the random distributed nature of these networks, battery replacement is a difficult task. In fact,a primary issue that prevents these networks to be used in many application areas is the short battery life. Therefore, maximizing the battery life time of the sensor nodes is important. Figure 1 shows the peak current consumption limit when a 950mAh battery is used as the energy source. As seen in the figure, battery life can vary by orders of magnitude depending on the duty cycle of each operation. To allow for higher maximum peak current, it is desirable to have the sensor remain in the off-state for as long as possible.However, the latency requirement of the system dictates how often the sensor needs to be active. For the industrial sensor application described above, the sensor needs to operate every 5ms to satisfy the latency requirement.Assuming that the sensor operates for 100µs every 5ms, the duty cycle is 2%. To achieve a one-year battery life, the peak current consumption must be kept under 5.4mA, which translates to approximately 10mW at 2V supply.This is a difficult target to achieve for sensors that communicate at giga-Hertz carrier frequencies.There has been active research in microsensor networks over the past years. Gupta [1] and Grossglauser [2] established information theoretic bounds on the capacity of ad-hoc networks. Chang [3] and Heinzelman [4] suggested algorithms to increase overall network life-time by spreading work loads evenly among all sensors. Much of the work in this area, especially those that deal with energy consumption of sensor networks, require an energy model [5]. This paper develops a realistic energy model based on the power consumption of a state of the art Bluetoothtransceiver [6]. This model provides insights into how to minimize the power consumption of sensor networks and can be easily incorporated into work that studies energy limited wireless sensor networks. The outline of this paper is as follows. Section II derives the transceiver model. Section III applies this model to analyzing the battery life time of the Bluetooth transceiver.Section IV investigates the dependencies in the model and shows how to modify the design of the Bluetooth transceiver to improve the battery life. Section V shows the battery life improvement realized by applying the results in Section IV. Section VI summarizes the paper.II. Microsensor Transceiver ModellingThis section derives a simple energy model for low power microsensors. Figure 2 shows the model of the sensor node.It includes a sensor/DSP unit for data processing, D/A and A/D for digital-to-analog and analog-to-digital conversion, and a wireless transceiver for data communication. The sensor/DSP, D/A, and A/D operate at low frequency and consume less than 1mW. This is over an order of magnitude less than the power consumption of the transceiver. Therefore, the energy model ignores the contributions from these components. The transceiver has three modes of operation: start-up, receive, and transmit. Each mode will be described and modelled.A. Start-up ModeWhen the transceiver is first turned on, it takes some time for the frequency synthesizer and the VCO to lock to the carrier frequency. The start-up energy can be modelled as follows:where P LO is the power consumption of the synthesizer and the VCO. The term t start is the required settling time. RF building blocks including PA, LNA, and mixer have negligible start-up time and therefore can remain in the off-state during the start-up mode.B. Receive ModeThe active components of the receiver includes the low noise amplifier (LNA), mixer, frequency synthesizer, VCO, intermediate-frequency (IF) amplifier (amp), and demodulator (Demod). The receiver energy consumption can be modelled as follows:where P RX includes the power consumption of the LNA,mixer, IF amplifier, and demodulator. The receiver power consumption is dictated by the carrier frequency and the noise and linearity requirements. Once these parameters are determined, to the first order the power consumption can be approximated as a constant, for data rates up to 10’s of Mb/s. In other words, the power consumption is dominated by the RF building blocks that operate at the carrier frequency. The IF demodulator power varies with data rate, but it can be made small by choosing a low IF.C. Transmit ModeThe transmitter includes the modulator (Mod), frequency synthesizer and VCO (shared with the receiver), and power amplifier (PA). The data modulates the VCO and produces a FSK signal at the desired data rate and carrier frequency. A simple transmitter energy model is shown in Equation (3). The modulator consumes very little energy and therefore can be neglected.P LO can be approximated as a constant. P PA depends on additional factors and needs to be modelled more carefully as follows:where η is the PA efficiency, r is the data rate, d is the transmission distance, and n is the path loss exponent. γPA is a factor that depends on E b /N O , noise factor F of the receiver, link margin L mar , wavelength of the carrier frequency λ, and th e transmit/receive antenna gains G T ,G R :From Equations (3) and (4), the transmitter power consumption can be written as a constant term plus a variable term. The energy model thus becomesIII. Bluetooth TransceiverHere we demonstrate how the above model can be used to calculate the battery life time of a Bluetooth transceiver [6]. This is one of the lowest power Bluetooth transceivers reported in literature. The energy consumption of the transceiver depends on how it operates. Assuming a 100-bit packet is received and a 100-bit packet is transmitted every 5ms, Figure 3 showsthe transceiver activity within one cycle of operation.The transceiver takes 120µs to start up. Operating at 1Mb/s, the receiver takes 100µs to receive the packet. The transceiver then switches to the transmit mode and transmits a same-length packet at the same rate. A 10µs interval, t switch , between the receive and the transmit mode is allowed to switch channel or to absorb any transient behavior. Therefore, the energy dissipated in one cycle of operation is simplyBoth the average power consumption and the duty cycle can be found From Figure 3. Knowing that the transceiver operates at 2V, the life time for a 950mAh battery is calculated to be approximately 2-months.IV. Energy OptimizationThe microsensor system described in Section I requires a battery life of one year or better. Although the Bluetooth transceiver described in the last section falls short of this requirement, it serves as a starting point for making improvements. This section examines E op in detail and suggests ways to increase the battery life by considering both circuit and system improvements. A.Start-up EnergyThe start-up energy can be a significant part of the total energy consumption, especially when the transceiver is used to send short packets in burst mode. For the Bluetooth transceiver, E start accounts for 20% of E op .The start-up energy becomes negligible if the following condition is held true:For the receive/transmit scheme shown in Figure 3, the right hand-side of Equation (8)is evaluated to be approximately 450µs. To keep E start an order of magnitude below E op , it is desirable to have a start-up time of less than 45µs. Cho has demonstrated a 5.8GHz frequency synthesizer im- plementation with a start-up time under 20µs [7].B. Power AmplifierThe PA power consumption is given bywhere η is the power efficiency and P out is the RF output power. P out can be determined by link-budget analysis. For a Bluetooth transceiver, the required P out is 1mW [8].This enables a maximum transmission distance of 10 meters, which is adequate for microsensor applications. Note that P out is small as compared to P LO . The Bluetooth transceiver discussed in Section II has a maximum RF output power of 1.6mW and a PA power consumption of 10mW, sothe efficiency is at 16%. At frequencies around 2GHz, the PA efficiency can vary from 10% [9] to 70% [10] depending on linearity, circuit topology, and technology. Since FSK signal has a constant envelope, nonlinea r PA’s can be used so that better efficiency can be achieved. As will be shown in the next section, PA efficiency has a significant impact on the battery life.C. Data RateAssuming a packet of length L pkt is transmitted at dat rate r, then the transmit time isThe transmitter energy consumption can be re-written asEquation (12) shows that the contribution of the fixed cost P LO can be reduced by increasing the data rate. The energy per bit, E bit , is defined as E op divided by the total number of bits received and sent during one cycle of operation. Assuming a packet of length L pkt is received and a packet of the same length is transmitted, E bit can be found by dividing Equation (7) by 2L pkt . Substituting the appropriate expressions for E start , E rx , and E tx and re-arranging the terms, we getThe first term in Equation (13) is the start-up energy cost. The second term is the PA energy cost. The third term is the cost of the rest of the transceiver electronics during the transmit and receive modes. Note that this term is divided by the data rate r. Figure 4 shows E bit as a function of data rate. The two solid curves have start-up time 120µs and PA efficiencies 10% and 70%, respectively. The two dotted curves have start-up time 20µs and efficiencies 10% and 70%, respectively. At low data rate, E bit is dominated by the fixed cost (the 3rd term in Equation (13)). At high data rate, the start-up energy and the PA energy dominates, so in order to increase battery life, good circuit design techniques need to be applied to minimize the start-up time and to maximize the PA efficiency.Figure 5 shows the impact of PA efficiency on the battery life at a data rate of 10Mb/s. At t start = 120µs, the startup energy is so large that the battery life is limited to 7month even if the PA reaches 100% efficiency. At t start =20µs, the battery life is much improved. The PA efficiency needs to be higher than about 30% to have a 1-year or better battery life. This is certainly achievable as discussed previously in the PA section.V. Performance ImprovementThere are three apparent results from the previous section. First, the data rate should be increased to reduce the fixed cost. Second, the start-up time should be minimized. Third, PA efficiency should be maximized. Figure 6 shows the transceiver activity for a transceiver that has 20µs start-up time and 10Mb/s data rate. The power consumption of the electronics are kept the same as in the Bluetooth transceiver except for the PA. The maximum RF output power is set at 10mW to accommodate the higher data rate, and the PA efficiency is assumed to be 50%. The switching time is kept at 10µs, although this is a conservative since the switching time is likely to be shorter for a faster frequency synthesizer. The E op of this transceiver is 8x lower than that of theBluetooth transceiver. The battery life-time extends from 2-months to approximately1.3 years.VI. ConclusionThis paper describes the modelling of short-range transceivers for wireless sensor applications. This model takes into account energy dissipation during the start-up, transmit, and receive modes. This model is first used to analyze the battery life of a state of the art Bluetooth transceiver, and then it is used to optimize E op . This paper shows that the battery life can be improved significantly by increasing the data rate, reducing the start-up time, and improving the PA efficiency. Increasing the data rate drives down the fixed energy cost of the transceiver. Reducing the start-up time decreases the start-up energy overhead. Improving the PA efficiency lowers the energy per bit cost of the PA.一个简单的能量无线微传感器的接收机模型摘要—本文描述了微传感器的近程的收发器的造型的应用程序。
传感器的基础知识中英文对照外文翻译文献
中英文对照外翻译Basic knowledge of transducersA transducer is a device which converts the quantity being measured into an optical, mechanical, or-more commonly-electrical signal. The energy-conversion process that takes place is referred to as transduction.Transducers are classified according to the transduction principle involved and the form of the measured. Thus a resistance transducer for measuring displacement is classified as a resistance displacement transducer. Other classification examples are pressure bellows, force diaphragm, pressure flapper-nozzle, and so on.1、Transducer ElementsAlthough there are exception ,most transducers consist of a sensing element and a conversion or control element. For example, diaphragms,bellows,strain tubes and rings, bourdon tubes, and cantilevers are sensing elements which respond to changes in pressure or force and convert these physical quantities into a displacement. This displacement may then be used to change an electrical parameter such as voltage, resistance, capacitance, or inductance. Such combination of mechanical and electrical elements form electromechanical transducing devices or transducers. Similar combination can be made for other energy input such as thermal. Photo, magnetic and chemical,giving thermoelectric, photoelectric,electromaanetic, and electrochemical transducers respectively.2、Transducer SensitivityThe relationship between the measured and the transducer output signal is usually obtained by calibration tests and is referred to as the transducer sensitivity K1= output-signal increment / measured increment . In practice, the transducer sensitivity is usually known, and, by measuring the output signal, the input quantity is determined from input= output-signal increment / K1.3、Characteristics of an Ideal TransducerThe high transducer should exhibit the following characteristicsa) high fidelity-the transducer output waveform shape be a faithful reproduction of the measured; there should be minimum distortion.b) There should be minimum interference with the quantity being measured; the presence of the transducer should not alter the measured in any way.c) Size. The transducer must be capable of being placed exactly where it is needed.d) There should be a linear relationship between the measured and the transducer signal.e) The transducer should have minimum sensitivity to external effects, pressure transducers,for example,are often subjected to external effects such vibration and temperature.f) The natural frequency of the transducer should be well separated from the frequency and harmonics of the measurand.4、Electrical TransducersElectrical transducers exhibit many of the ideal characteristics. In addition they offer high sensitivity as well as promoting the possible of remote indication or mesdurement. Electrical transducers can be divided into two distinct groups:a) variable-control-parameter types,which include:i)resistanceii) capacitanceiii) inductanceiv) mutual-inductance typesThese transducers all rely on external excitation voltage for their operation.b) self-generating types,which includei) electromagneticii)thermoelectriciii)photoemissiveiv)piezo-electric typesThese all themselves produce an output voltage in response to the measurand input and their effects are reversible. For example, a piezo-electric transducer normally produces an output voltage in response to the deformation of a crystalline material; however, if an alternating voltage is applied across the material, the transducer exhibits the reversible effect by deforming or vibrating at the frequency of the alternating voltage.5、Resistance TransducersResistance transducers may be divided into two groups, as follows:i) Those which experience a large resistance change, measured by using potential-divider methods. Potentiometers are in this group.ii)Those which experience a small resistance change, measured by bridge-circuit methods. Examples of this group include strain gauges and resistance thermometers.5.1 PotentiometersA linear wire-wound potentiometer consists of a number of turns resistance wire wound around a non-conducting former, together with a wiping contact which travels over the barwires. The construction principles are shown in figure which indicate that the wiperdisplacement can be rotary, translational, or a combination of both to give a helical-type motion. The excitation voltage may be either a.c. or d.c. and the output voltage is proportional to the input motion, provided the measuring device has a resistance which is much greater than the potentiometer resistance.Such potentiometers suffer from the linked problem of resolution and electrical noise. Resolution is defined as the smallest detectable change in input and is dependent on thecross-sectional area of the windings and the area of the sliding contact. The output voltage is thus a serials of steps as the contact moves from one wire to next.Electrical noise may be generated by variation in contact resistance, by mechanical wear due to contact friction, and by contact vibration transmitted from the sensing element. In addition, the motion being measured may experience significant mechanical loading by the inertia and friction of the moving parts of the potentiometer. The wear on the contacting surface limits the life of a potentiometer to a finite number of full strokes or rotations usually referred to in the manufacture’s specification as the ‘number of cycles of life expectancy’, a typical value being 20*1000000 cycles.The output voltage V0 of the unload potentiometer circuit is determined as follows. Let resistance R1= xi/xt *Rt where xi = input displacement, xt= maximum possible displacement, Rt total resistance of the potentiometer. Then output voltage V0= V*R1/(R1+( Rt-R1))=V*R1/Rt=V*xi/xt*Rt/Rt=V*xi/xt. This shows that there is a straight-line relationship between output voltage and input displacement for the unloaded potentiometer.It would seen that high sensitivity could be achieved simply by increasing the excitation voltage V. however, the maximum value of V is determined by the maximum power dissipation P of the fine wires of the potentiometer winding and is given by V=(PRt)1/2 .5.2 Resistance Strain GaugesResistance strain gauges are transducers which exhibit a change in electrical resistance in response to mechanical strain. They may be of the bonded or unbonded variety .a) bonded strain gaugesUsing an adhesive, these gauges are bonded, or cemented, directly on to the surface of the body or structure which is being examined.Examples of bonded gauges arei) fine wire gauges cemented to paper backingii) photo-etched grids of conducting foil on an epoxy-resin backingiii)a single semiconductor filament mounted on an epoxy-resin backing with copper or nickel leads.Resistance gauges can be made up as single elements to measuring strain in one direction only,or a combination of elements such as rosettes will permit simultaneous measurements in more than one direction.b) unbonded strain gaugesA typical unbonded-strain-gauge arrangement shows fine resistance wires stretched around supports in such a way that the deflection of the cantilever spring system changes the tension in the wires and thus alters the resistance of wire. Such an arrangement may be found in commercially available force, load, or pressure transducers.5.3 Resistance Temperature TransducersThe materials for these can be divided into two main groups:a) metals such as platinum, copper, tungsten, and nickel which exhibit and increase in resistance as the temperature rises; they have a positive temperature coefficient of resistance.b) semiconductors, such as thermistors which use oxides of manganese, cobalt, chromium, or nickel. These exhibit large non-linear resistance changes with temperature variation and normally have a negative temperature coefficient of resistance.a) metal resistance temperature transducersThese depend, for many practical purpose and within a narrow temperature range, upon the relationship R1=R0*[1+a*(b1-b2)] where a coefficient of resistance in ℃-1,and R0 resistance in ohms at the reference temperature b0=0℃ at the reference temperature range ℃.The international practical temperature scale is based on the platinum resistance thermometer, which covers the temperature range -259.35℃ to 630.5℃.b) thermistor resistance temperature transducersThermistors are temperature-sensitive resistors which exhibit large non-liner resistance changes with temperature variation. In general, they have a negative temperature coefficient. For small temperature increments the variation in resistance is reasonably linear; but, if large temperature changes are experienced, special linearizing techniques are used in the measuring circuits to produce a linear relationship of resistance against temperature.Thermistors are normally made in the form of semiconductor discs enclosed in glass vitreous enamel. Since they can be made as small as 1mm,quite rapid response times are possible.5.4 Photoconductive CellsThe photoconductive cell , uses a light-sensitive semiconductor material. The resistance between the metal electrodes decrease as the intensity of the light striking the semiconductor increases. Common semiconductor materials used for photo-conductive cells are cadmium sulphide, lead sulphide, and copper-doped germanium.The useful range of frequencies is determined by material used. Cadmium sulphide is mainly suitable for visible light, whereas lead sulphide has its peak response in the infra-red regionand is, therefore , most suitable for flame-failure detection and temperature measurement. 5.5 Photoemissive CellsWhen light strikes the cathode of the photoemissive cell are given sufficient energy to arrive the cathode. The positive anode attracts these electrons, producing a current which flows through resistor R and resulting in an output voltage V.Photoelectrically generated voltage V=Ip.RlWhere Ip=photoelectric current(A),and photoelectric current Ip=Kt.BWhere Kt=sensitivity (A/im),and B=illumination input (lumen)Although the output voltage does give a good indication of the magnitude of illumination, the cells are more often used for counting or control purpose, where the light striking the cathode can be interrupted.6、Capacitive TransducersThe capacitance can thus made to vary by changing either the relative permittivity, the effective area, or the distance separating the plates. The characteristic curves indicate that variations of area and relative permittivity give a linear relationship only over a small range of spacings. Thus the sensitivity is high for small values of d. Unlike the potentionmeter, the variable-distance capacitive transducer has an infinite resolution making it most suitable for measuring small increments of displacement or quantities which may be changed to produce a displacement.7、Inductive TransducersThe inductance can thus be made to vary by changing the reluctance of the inductive circuit. Measuring techniques used with capacitive and inductive transducers:a)A.C. excited bridges using differential capacitors inductors.b)A.C. potentiometer circuits for dynamic measurements.c) D.C. circuits to give a voltage proportional to velocity for a capacitor.d) Frequency-modulation methods, where the change of C or L varies the frequency of an oscillation circuit.Important features of capacitive and inductive transducers are as follows:i)resolution infiniteii) accuracy+- 0.1% of full scale is quotediii)displacement ranges 25*10-6 m to 10-3miv) rise time less than 50us possibleTypical measurands are displacement, pressure, vibration, sound, and liquid level.8、Linear Variable-differential Ttransformer9、Piezo-electric Transducers10、Electromagnetic Transducers11、Thermoelectric Transducers12、Photoelectric Cells13、Mechanical Transducers and Sensing Elements传感器的基础知识传感器是一种把被测量转换为光的、机械的或者更平常的电信号的装置。
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传感器外文翻译文献(文档含中英文对照即英文原文和中文翻译)译文：传感器的基础知识传感器是一种将能量转化为光的、机械的或者更为普遍的电信号，这种能量转换发生的过程称之为换能作用。
按照能量转换的复杂程度和控制方式，传感器被分为不同的等级，用来测量位移的电阻式传感器被分类为电阻式位移传感器，其他的分类诸如压力波纹管、压力膜和压力阀等。
1、传感器元件大多数的传感器是由感应元件，转换元件、控制元件、当然也有例外，例如：震动膜、.波纹管、应力管和应力环、低音管和悬臂都是敏感元件。
对物理量作出反应，将物理的压力和力转换为位移，这些转换量可以被用作电参数，如电压、电阻、电容或者感应系数。
机械式和电子式元件合并形成机电式传感设备或传感器。
相似量的结合可以作为能量输入例如：热的、光的、磁的、化学的相互结合产生的热电式、光电式、电磁式和电化学式传感器。
2、传感器灵敏度通过校正测量系统获得的被测物理量和传感器输出信号的关系叫做传感器灵敏度K1=输出信号增量∕被测量的增量，实际上，传感器的灵敏度是已知的通过测量输出信号，输入量由下式决定，输入量=输出信号的增量∕k1。
3、理想传感器的性能特点：a)高保真性：传感器的输出波形式对被测量的真实展现，并且失真很小。
b)被测量干扰最小，任何情况下传感器的精度不能改变。
c)尺寸：必须将传感器正确的放在所需要的场所。
d)被测量和传感器信号之间要有线性关系。
e)传感器对外部变换由很小的灵敏度,例如：压力传感器常常受到外部震动和环境温度的影响f)传感器的固有频率应能够避开被测量的频率和谐波。
4、电传感器电传感器由很多理想特性，它们不仅实现远程测量和显示，还能提供高灵敏度。
电传感器可分为如下两大类。
这些传感器依靠外界电压刺激来工作。
A、变参数型包括：ⅰ）电阻式ⅱ）电容式ⅲ）感应式ⅳ）自感应式ⅴ）互感应式B、自激型包括:ⅰ)电磁式；ⅱ）热电式ⅲ）光栅式；ⅳ）压电式。
这些传感器都是自己产生输出电压来反映被测量的输入并且这些过程是可逆的;例如，一般的电子传感器通常能产生出输出电压来反映晶体材料的性能，.然而，如果在材料上加一个自变电压，传感器可以通过变形或与变电压同频率的振动来体现可逆效应。
5、电阻式传感器分类：ⅰ）那些表现为大电阻变化的物理量可通过分压方式进行测量，电位器就属于此类。
ⅱ）那些表现为小电阻变化的物理量可以通过电桥电路的方式来测量，这一类包括应变仪和电阻温度计。
5.1、电位器绕线式电位器由许多绕在非导体骨架的电阻丝以及滑行在线圈上的触头组成。
结构原理如图，触头能够转动、直线式运动或者两运动合成的螺旋式运动。
如果测量设备的电阻比电位器的电阻大，那么电压既可以是交流也可以是直流，且输出电压与输入运动成正比。
这种电位器受到分辨率和电噪声的影响，电噪声被定义为能检测到的输入量的最小的变化，电噪声分辨率大小取决于线圈与滑动触头围成的面积因此，输出电压为触头从一端移到另一端时一系列阶跃。
电子噪声可以通过接触电阻的振动、触头摩擦形成的机械磨损以及从敏感元件传出的触头振动产生。
另外，测得的运动量可以通过惯性和电位器中移动元件的摩擦获得较大的机械载荷。
触头表面的磨损将电位器的寿命限制为多少转。
通常指的是生产商在说明书中提及的“寿命转数”，一个典型值为20*1000000转,空载电位器电路的输出电压V0由下式决定：设电阻R1= xi/at *Rat，其中xi为输入位移，at为最大可能位移，Rat为电位器的电阻。
那输入电压为V*R1/(R1+( Rt-R1))=V*R1/Rt=V*xi/at*Retort=V*xi/it 上式表明，对于空载电位器输出电压和输入位移呈直线关系,通过提高激励电压V可以获得高的灵敏度,但是，V的最大值由电位器线圈金属丝的功率损耗P决定，即V=(Part)1/2。
5.2、电阻应变仪电阻应变仪是由机械应变产生电阻变化的传感器。
它们是耦合或者非耦合的。
a）耦合应变仪运用黏合剂可将应变仪与被检测的结构或部件的表面粘合或粘牢。
耦合应变仪分为：ⅰ)粘合在绝缘纸背后的金属细丝仪ⅱ）在环氧树脂上粘贴导电箔片的光栅ⅲ）在环氧树脂上粘贴铜或镍的半导体丝电阻应变仪可作为单个元件仅在一个方向测量应力，或者几个元件的组合体可在几个方向同时进行测量。
b）非耦合应变仪：典型应变仪表明细电阻丝在悬臂弹簧偏差作用下改变电阻丝张力进而改变电阻丝的阻值。
商业上通常在力、负载、压力传感器上运用此方法。
5.3、电阻温度传感器分类：a)金属（如铂、铜、钨、镍）的阻值会随着温度的升高而增大，即有一个正温度电阻系数。
b)半导体，如用锰、钴、铬或镍的氧化物制成的电热调节器，其阻值变化与温度变化存在一个非线性关系，即通常有一个负温度电阻系数。
c)金属电阻温度传感,在窄温度变化范围内，此类传感器取决于以下关系：R1=R0[1+a(b1-b0)]，式中，a阻抗系数，R0为b0=0°时C的电阻。
d)电热调节器（半导体）电阻温度传感器。
电热调节器为感温电阻器，其阻值变化与温度变化呈非线性关系。
通常此类传感器有一负温度系数。
对于小的温度增量，阻值的变化大体呈线性，但是如果存在大的温差，测量电路需运用特定线性化技术生成电阻随温度变化的线性关系。
电热调节器通常被制成附有玻璃质釉的半导体圆盘形状，由于电热调节器可以小到1mn，所以响应的时间非常快。
5.4、光敏元件光敏元件采用光敏半导体材料做成。
当照射在半导体上的光强度增大，金属电极间的阻抗就会降低。
光敏元件常用的半导体材料有硫化镉、硫化铅和铜锗化合物。
频率的有效范围由所用材料决定。
硫化镉主要适用于可见光，硫化铅在红外线区有峰值响应，所以最适合于光故障检测以及温度测量。
5.5、放射性光元件当光照射到放射性光元件的阴极时，电子就会获取足够能量到达阴极。
阴极就会吸收这些电子产生一个通过电阻R的电流，从而形成一输出电压V。
产生的光电压V=I.R式中，I为光发射电流，I=K.B且为灵敏度，B输入照度（lm），尽管输出电压能够表示照明的强度，这类元件却更多的应用于计算或调节，这里照射到阴极的光可被中断。
6、电容式传感器电容量随着相对介电常数、截面面积、或者极板间的距离的变化而变化。
电容的特征曲线表明，在空间的一段范围内，截面面积和相对介电常数的变化与电容量变化成线性关系。
不象电位器，变极距型电容传感器有无限的分辨率，这最适合测量微小的位移增量的位移。
7、电感式传感器电感可以通过改变电感电路的阻抗来调节,电容式和电感式传感器的测量技术：a）用差分式电容或电感作为交流电桥。
b）用交流电位计电路做动态测量。
c）用直流电路为电容器提供正比于容值变化的电压。
d）采用调频法，C或者L随着振荡电路频率的变化而改变电容式和电感式传感器的一些重要特性如下：ⅰ)分辨率无限ⅱ）精确到满量程的+-0.1%ⅲ）位移范围从25*10-6m到10-3mⅳ）上升时间小于50us典型的被测量是位移、压力、振动量、声音和液位。
8、线性调压器9、压电式传感器10、电磁式传感器11、热电式传感器12、光电管13、机械式传感器及敏感元件Basic knowledge of transducersA transducer is a device which converts the quantity being measured into an optical, mechanical, or-more commonly-electrical signal. The energy-conversion process that takes place is referred to as transduction.Transducers are classified according to the transduction principle involved and the form of the measured. Thus a resistance transducer for measuring displacement is classified as a resistance displacement transducer. Other classification examples are pressure bellows, force diaphragm, pressure flapper-nozzle, and so on.1、Transducer ElementsAlthough there are exception ,most transducers consist of a sensing element and a conversion or control element. For example, diaphragms bellows strain tubes and rings, bourdon tubes, and cantilevers are sensing elements which respond to changes in pressure or force and convert these physical quantities into a displacement. This displacement may then be used to change an electrical parameter such as voltage, resistance, capacitance, or inductance. Such as combination of mechanical and electrical elements form electromechanical transduction devices or transducers. Similar combination can be made for other energy input such as thermal. Photo, magnetic and chemical giving thermoelectric, photoelectric electromagnetic and electrochemical transducers respectively.2、Transducer SensitivityThe relationship between the measured and the transducer output signal is usually obtained by calibration tests and is referred to as the transducer sensitivity K1= output-signal increment / measured increment . In practice, the transducer sensitivity is usually known, and, by measuring the output signal, the input quantity is determined from input= output-signal increment / K1.3、Characteristics of an Ideal TransducerThe high transducer should exhibit the following characteristicsa) high fidelity-the transducer output waveform shape be a faithful reproduction of the measured; there should be minimum distortion.b) There should be minimum interference with the quantity being measured; the presence ofthe transducer should not alter the measured in any way.c) Size. The transducer must be capable of being placed exactly where it is needed.d) There should be a linear relationship between the measured and the transducer signal.e) The transducer should have minimum sensitivity to external effects, pressure transducers for example are often subjected to external effects such vibration and temperature.f) The natural frequency of the transducer should be well separated from the frequency and harmonics of the measured.4、Electrical TransducersElectrical transducers exhibit many of the ideal characteristics. In addition they offer high sensitivity as well as promoting the possible of remote indication or measurements. Electrical transducers can be divided into two distinct groups:a) variable-control-parameter types, which include:I) resistanceii)capacitanceiii)inductanceiv) mutual-inductance typesThese transducers all rely on external excitation voltage for their operation.b) self-generating types, which includeI) electromagneticii) thermoelectriciii) photo emissiveIV)piano-electric typesthese all themselves produce an output voltage in response to the measured input and their effects are reversible. For example, a piano-electric transducer normally produces an output voltage in response to the deformation of a crystalline material; however, if an alternating voltage is applied across the material, the transducer exhibits the reversible effect by deforming or vibrating at the frequency of the alternating voltage.5、Resistance TransducersResistance transducers may be divided into two groups, as follows:I) Those which experience a large resistance change, measured by using potential-divider methods. Potentiometers are in this group.ii) Those which experience a small resistance change, measured by bridge-circuit methods. Examples of this group include strain gauges and resistance thermometers.5.1 Potentiometersa linear wire-wound potentiometer consists of a number of turns resistance wire wound around a non-conducting former, together with a wiping contact which travels over the barbwires. The construction principles are shown in figure which indicate that the wiper displacement can be rotary, translational or a combination of both to give a helical-type motion. The excitation voltage may be either act. Or deco. And the output voltage is proportional to the input motion, provided the measuring device has a resistance which is much greater than the potentiometer resistance.Such potentiometers suffer from the linked problem of resolution and electrical noise. Resolution is defined as the smallest detectable change in input and is dependent on the cross-sectional area of the windings and the area of the sliding contact. The output voltage is thus a serial of steps as the contact moves from one wire to next.Electrical noise may be generated by variation in contact resistance, by mechanical wear due to contact friction, and by contact vibration transmitted from the sensing element. In addition, the motion being measured may experience significant mechanical loading by the inertia and friction of the moving parts of the potentiometer. The wear on the contacting surface limits the life of a potentiometer to a finite number of full strokes or rotations usually referred to in the manufacture’s specification as the ‘number of cycles of life expectancy’, a typical value being 20*1000000 cycles.The output voltage V0 of the unload potentiometer circuit is determined as follows. Let resistance R1= xi/ox *Rat where xi = input displacement, at= maximum possible displacement, Rat total resistance of the potentiometer. Then output voltage V0= V* R1/ (R1+ (Rt-R1)) =V*R1/Rt=V*xi/at*Retort=V*xi/it. This shows that there is a straight-line relationship between output voltage and input displacement for the unloaded potentiometer.It would seen that high sensitivity could be achieved simply by increasing the excitation voltage V. however, the maximum value of V is determined by the maximum power dissipation P of the fine wires of the potentiometer winding and is given by V=(Part)1/2 .5.2 Resistance Strain GaugesResistance strain gauges are transducers which exhibit a change in electrical resistance in response to mechanical strain. They may be of the bonded or unbounded variety.a) Bonded strain gaugesusing an adhesive, these gauges are bonded, or cemented, directly on to the surface of the body or structure which is being examined.Examples of bonded gauges areI) fine wire gauges cemented to paper backingii) photo-etched grids of conducting foil on an epoxy-resin backingiii) a single semiconductor filament mounted on an epoxy-resin backing with copper or nickel leads.Resistance gauges can be made up as single elements to measuring strain in one direction only, or a combination of elements such as rosettes will permit simultaneous measurements in more than one direction.b) Unbounded strain gaugesa typical unbounded-strain-gauge arrangement shows fine resistance wires stretched around supports in such a way that the deflection of the cantilever spring system changes the tension in the wires and thus alters the resistance of wire. Such an arrangement may be found in commercially available force, load, or pressure transducers.5.3 Resistance Temperature TransducersThe materials for these can be divided into two main groups:a) metals such as platinum, copper, tungsten, and nickel which exhibit and increase in resistance as the temperature rises; they have a positive temperature coefficient of resistance.b) Semiconductors, such as thermostats which use oxides of manganese, cobalt, chromium, or nickel. These exhibit large non-linear resistance changes with temperature variation and normally have a negative temperature coefficient of resistance.a) Metal resistance temperature transducersthese depend, for many practical purpose and within a narrow temperature range, upon the relationship R1=R0*[1+a*(b1-b2)] where a coefficient of resistance in ℃-1, and R0 resistance in ohms at the reference temperature b0=0℃ at the reference temperature range ℃. The international practical temperature scale is based on the platinum resistance thermometer, which covers the temperature range -259.35℃ to 630.5℃.b) Thermostat resistance temperature transducersThermostats are temperature-sensitive resistors which exhibit large non-liner resistance changes with temperature variation. In general, they have a negative temperature coefficient. For small temperature increments the variation in resistance is reasonably linear; but, if large temperature changes are experienced, special linear zing techniques is used in the measuring circuits to produce a linear relationship of resistance against temperature.Thermostats are normally made in the form of semiconductor discs enclosed in glass vitreousenamel. Since they can be made as small as 1mm, quite rapid response times are possible.5.4 Photoconductive CellsThe photoconductive cell, uses a light-sensitive semiconductor material. The resistance between the metal electrodes decreases as the intensity of the light striking the semiconductor increases. Common semiconductor materials used for photo-conductive cells are cadmium supplied, lead supplied, and copper-doped germanium.The useful range of frequencies is determined by material used. Cadmium sapphire is mainly suitable for visible light, whereas lead supplied has its peak response in the infra-red region and is, therefore, most suitable for flame-failure detection and temperature measurement.5.5 Photo emissive CellsWhen light strikes the cathode of the photo emissive cell are given sufficient energy to arrive the cathode. The positive anode attracts these electrons, producing a current which flows through resistor R and resulting in an output voltage V.Photo electrically generated voltage V=PurlWhere Imp=photoelectric current(A),and photoelectric current Imp=Kat’sWhere Kt=sensitivity (A/imp),and B=illumination input (lumen)Although the output voltage does give a good indication of the magnitude of illumination, the cells are more often used for counting or control purpose, where the light striking the cathode can be interrupted.6、Capacitive TransducersThe capacitance can thus made to vary by changing either the relative permittivity, the effective area, or the distance separating the plates. The characteristic curves indicate that variations of area and relative permittivity give a linear relationship only over a small range of spacing’s. Thus the sensitivity is high for small values of d. Unlike the potentiometer, the variable-distance capacitive transducer has an infinite resolution making it most suitable for measuring small increments of displacement or quantities which may be changed to produce a displacement.7、Inductive TransducersThe inductance can thus be made to vary by changing the reluctance of the inductive circuit.Measuring techniques used with capacitive and inductive transducers:a) A.C. excited bridges using differential capacitors inductors.b）A.C. potentiometer circuits for dynamic measurements.c ) D.C. circuits to give a voltage proportional to velocity for a capacitor.d）Frequency-modulation methods, where the change of C or L varies the frequency of an oscillation circuit.Important features of capacitive and inductive transducers are as follows:I) resolution infiniteii)accuracy+- 0.1% of full scale is quotediii)displacement ranges 25*10-6 m to 10-3miv)rise time less than 50us possibleTypical misbrands are displacement, pressure, vibration, sound, and liquid level.8、Linear Variable-differential Transformer9、Pies-electric Transducers10、Electromagnetic Transducers11、Thermoelectric Transducers12、Photoelectric Cells13、Mechanical Transducers and Sensing Elements。