第三章补充习题

1.Eddy current proximity switch may detect the proximity of ___________.

A. human body

B. water

C. metal component

D. plastic component

电涡流接近开关可以利用电涡流原理检测出____________的靠近程度。

A．人体B．水C．金属零件D．塑料零件

2.When eddy current coil approaches the metal board, the equivalent inductance L of the coil

__________, the frequency of the FM converting circuit f _______________.

A. keeps constant

B. increases

C. decreases

当电涡流线圈靠近金属板材后，线圈的等效电感L__________，调频转换电路的输出频率f_______________。

A．不变B．增大C．减小

3. To measure the rotate speed of a gear whose no. of teeth z=60, the measured frequency

f=400Hz, the rotate speed of the gear n=______ r/min.

用电涡流传感器测量齿数z=60的齿轮的转速，测得f=400Hz，则该齿轮的转速n=______ r/min。

4.In the interspace between two parallel plates, inserting _________ could obtain the maximal

capacity.

A. plastic film

B. dry paper

C. wet paper

D. glass slice

在两片间隙为1mm的两块平行极板的间隙中插入________，可测得的最大的电容量。

A．塑料薄膜B．干的纸C．湿的纸D．玻璃薄片

5.In the FM measurement circuit of capacity sensor, ___________.

A. the capacity and the inductance are variables

B. the capacity is variable, the inductance

is constant C. the capacity is constant, the inductance is variable D. the capacity and the inductance are constants

在电容传感器中，若采用调频法测量转换电路，则电路中__________。

A．电容和电感均为变量B．电容是变量，电感量保持不变

C．电容保持常数，电感为变量D．电容和电感均保持不变

6.The supplemental inflatable restraint system (SRS) in automobile uses ________ to measure

the bump.

A. gas sensor

B. humidity sensor

C. variable differential transformer sensor

D. capacity accelerator sensor

轿车的保护气囊可用_________来测量。

A．气敏传感器B．湿敏传感器C．差动变压器D．电容式加速度传感器

7.In the measurement circuit to measure the light, the photosensitive diodes are _______ biased

connected while the photocells are usually _______ biased connected.

A. forward

B. backward

C. none

光敏二极管在测光电路应处于________偏置状态，而光电池通常处于_______偏置状态。

A．正向B．反向C．零

8.Photosensitive diode applies the ________ Effect while the photocell applies the

_______Effect.

A. External

B. Internal

C. Photovoltaic

光敏二极管属于________，光电池属于__________。

A．外光电效应B．内光电效应C．光生伏特效应

9.When the temperature increases, the dark currents of the LDR, photosensitive diode and the

photosensitive transistor will _________.

A.increase

B. decrease

C. keep constant

温度上升，光敏电阻、光敏二极管和光敏晶体管的暗电流__________。

A．上升B．下降C．不变

10.To charge the mobile phone with photocell, the photocells should be ________ to increase the

voltage firstly, then ________ to increase the output current.

A. connected in series

B. connected in parallel

C. shorted connected

D. open connected

欲利用光电池为手机充电，需将几片光电池______起来，以提高输出电压，再将几组光电池_______起来，以提高输出电流。

A．串联B．并联C．短路D．开路

11.To precisely measure the illumination of weak light, the photocell should be connected with

____________.

A. voltage amplifier

B. A/D converter

C. charge amplifier

D. I/U converter

欲精密测量光的微弱照度，光电池应配接_____________。

A．电压放大器B．A/D转换器C．电荷放大器D．I/U转换器

12. Variable Gap Self-inductance Sensor adopts differential structure in order to (变隙式自感传感器采用差动结构是为了)_____________。

A．Add the length of the coil so that extend the scope of linearity (加长线圈的长度从而增加线性范围)

B．Improve the sensitivity and decrease temperature floating (提高灵敏度，减小温漂) C．Reduce the cost (降低成本)

D．Increase the magnetism of the coil to the ferromagnetic core (增加线圈对衔铁的吸引力)

13. Self-inductance Sensor or Differential Transformer adopts phase-sensitive detector circuit in order to (自感传感器或差动变压器采用相敏检波电路主要的目的是为了)_______________。A．Improve sensitivity (提高灵敏度)

B．Convert the AC output signal into DC output signal (将输出的交流信号转换为直流信号) C．Reflect the phase and amplitude of the AC signal with the DC voltage output (使检波后的直流电压能反映检波前交流信号的相位和幅度)

14. A 2-wire 4-20mA Pressure Transmitter, the scope of scale is 0～1MPa, Please:

1) Give the expression between pressure p and current I.

2) Sketch the characteristic curve between pressure p and current I.

3) Calculate the current I when p equals to 0 MPa, 1 MPa and 0.5 MPa, respectively.

4) Calculate the load resistance R L to convert the output from current signal into voltage signal.

5) Calculate the pressure p when the current I is 5 mA.

6) Sketch the circuit diagram of the 2-wire 4-20 mA Pressure Transmitter. (The voltage of the power supply is 24 Volt DC)

(有一台两线制压力变送器，量程范围为0～1MPa，对应的输出电流为4～20mA。求：

1）压力p与输出电流I的关系表达式。（输入/输出方程）。

2）画出压力与输出电流间的输入/输出特性曲线。

3）当p为0 MPa,1 MPa 和 0.5 MPa 时变送器的输出电流。

4）如果希望在信号传输终端将电流信号转换为1～5V 电压，求负载电阻R L的阻值。

5）如果测得变送器的输出电流为5 mA，求此时的压力p。

6）画出该两线制压力变送器的接线电路图（电源电压为24伏）。)