气体检测1

Measurement Techniques, Vol. 43, No. 1, 2000
A MULTIFUNCTIONAL AND AIR TEMPERATURE
ATMOSPHERIC SENSOR
PRESSURE
A. E Aleinikov
U D C 621.317.39
The operating principle of a sensor for simultaneously measuring atmospheric pressure and air temperature using a semiconductor material with a transverse piezoelectric emf is considered. A method of investigating the metrological characteristics of the sensor and test results are presented.
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,-.,Biblioteka ff /Fig. 1. Construction of the multifunctional sensor: 1) cylindrical container, 2) integral strain-sensitive transducer with membrane, 3) spring threaded cylindrical bushing, 4) electrical leads of the integral strain-sensitive transducer, 5) current collector of foil-covered getinaks with contact areas 6, 7) guard tube, 8) electrical output cable.
The design of new sensors and the improvement of existing ones is a constant and important trend in measurement techniques [1]. A new class of sensors, which can be called multifunctional sensors [2] has been developed in recent years. The main feature of these sensors and the purpose of their design is the fact that they can reproduce and convert several quantities, acting in a small volume of space, into measurable signals [3]. The possibility of a cross correlation of the signals when measuring several quantities with such sensors enables the accuracy of measurements of these quantities to be increased and enables unstable materials, with a high degree of sensitivity to the input quantities, to be used as sensitive elements. The operating principle of the proposed multifunctional atmospheric pressure and air temperature sensor is based on the transverse piezoelectric emf effect (see the figure) [4, 5]. When anisotropic deformation occurs, nondiagonal components arise in the electrical conductivity tensor of germanium or silicon, and when a current flows in the direction of one of the edges of a rectangular sample, a potential difference U, called the transverse piezoelectric emf, arises on the opposite perpendicular faces. Taking into account the ratio of the sides of a rectangular strain-sensitive layer and the width of the potential contacts, the following formula was derived in [4] by analogy with boundary-value problems of the theory of Hall plates: U = qkrd/hc, where q is the intensity of the load of the distributed pressure, k is a coefficient which depends on the ratio of the dimensions of the strain converter and the potential contacts, r~ is a component of the resistance tensor, I is the current strength, h is the thickness of the strain-sensitive layer, and c is the electrical conductivity of the material of the sensitive element of the sensor. The results of investigations show that the resistance of such a structure has a pronounced temperature dependence [4, 5]. The method of investigating the metrological characteristics of the sensor reduces to determining the static characteristic of the pressure and temperature converters, their nonlinearity, and the variations of the output voltage [5]. When determining the static characteristic of the sensor as a pressure transducer, the tbllowing main operations were carried out: - the output of the voltage source was connected to a strain transducer, - using a transit connecting piece, the sensor was connected to a type AZD-2.5-T10 normalised pressure generator of accuracy class 0.05; - using the generator, normalised pressures in the range from 39.2 to 9.8 kPa (440--810 mm Hg) were discretely established; - after plotting the static characteristic of the pressure transducer under normal conditions, the sensor was placed in a temperature-controlled chamber, where this characteristic was plotted for different values of the temperature in the range from --40~ to +40~ The corresponding conversion coefficients were calculated over sections of the operating range between verified points (the ratio of the increment of the mean value of the output voltage to the increment of the input pressure causing it).
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the current was set at 1 m A using the f'trst resistance box and a voltage source: and, maintaining a current through the sen-
- the temperature in the temperature-controlled chamber was set at -40~ the terminals of the second resistance box;
Translated from Izmeritel'naya Tekhnika, No. 1, pp. 31-32, January, 2000. 44 0543-1972/00/4301-0044525.00 9 Kluwer Academic/Plenum Publishers