SU1560999A1 - Photoelectric pressure transducer - Google Patents

Abstract

The invention can be used in measurement technology, in technological control systems. The purpose of the invention is to expand the linear range of the output signal and increase the sensitivity of the sensor - is achieved by the fact that the photoelectric sensor, comprising a housing with a light guide 4 fixed on an elastic beam 3 and a radiation source 5, is equipped with a phototransistor 6, which is a MIS transistor with a gate circuit photo battery consisting of series-connected isolated PN junctions, as well as a feedback capacitor connected between the gate and the source of the MOS transistor, which changes its capacitance depending on spines from measured pressure. The capacitor is formed by an elastic beam 3 and a plate 7. This capacitor performs the function of a nonlinear load for the photo battery that controls the operation of the MOS transistor, which results in an expansion of the linear range and an increase in the sensitivity of the sensor in the range of the measured pressure. 6 Il.

Description

& /. /

The invention relates to a measurement technique and can be used to measure pressure.

The purpose of the invention is to expand the measurement range and increase the sensitivity of the sensor.

Figure 1 shows the construction of the sensor j in Figure 2 - the circuit for incorporating its elements into the electrical circuit of Figure 3; the positional characteristic of the photoelectric sensor; 4 is an equivalent electrical circuit of the sensor; FIG. 3 shows a family of volt-photo characteristics of a photo battery with different load impedances; FIG. 6 shows the photo-EMF photocell dependence on the axis of value (displacement).

A movable rod 2 is inserted into the opening of the housing 1, which transmits a concentrated force to the end of the elastic cantilever beam 3. A light guide 4 is attached to the beam 3, through which light comes from the radiation source 5 to the receiving plate 6. The fixed plate 7 forms one of the plates of the reverse capacitor connection C0. The second plate of the feedback capacitor is an elastic} beam 4.

Under the action of a force applied to the rod 3 as a result of bending deformation, the end of the beam 3, together with the end of the light guide 4, describes an arc in space. A beam of light emanating from the end of the light guide 4 moves along the surface of the photosensitive region of the photodetector 6.

The photodetector b is a metal-dielectric-semiconductor (MOSFET) zero-transistor and a photocell battery included in the gate circuit of the MOS transistor. The photo emf produced on a photo battery under illumination controls the operation of the MOS transistor, the output of which depends on the illumination.

The dependence of the output electric signal on the displacement (positional characteristic) is presented in FIG.

The most convenient for measuring is the range of motion variation, in which the output signal of the sensor is close to the linear function l Bblx kx, where U ayh is the output voltage, - x is the displacement; k - coefficient. The range of linear variation of the output signal is expanded by switching on between the gate and the source of the MOSFET of the feedback capacitor Cc. In this case, the impedance of the load of the circuit in which the photocell is included consists of the gate impedance — the source of the MOSFET Z zm and

g impedance capacitance wasp (fig.Z). The parameters of the capacitance C0 and MIS transistor are chosen so that the relation Z oc «Z,„ is fulfilled. When illuminating the photo battery with a variable luminous flux

5 photo-emf arising on a photo battery is also variable. For a variable photo-emf, a capacitor C0 in the photo-battery circuit is a shunt load connected in parallel to the gate of the MIS transistor. In this case, the photo-EMF applied to the gate of the MIS transistor is determined by the impedance of the capacitor C 0. Figure 4 shows the family of volt-x characteristics of the photo-battery at different load impedances. The greater the load impedance in the photo battery circuit, the greater its photo-emf.

Under the influence of concentrated force

0 F, an elastic bending deformation of the beam 3 occurs, which leads to a change in the luminance of the photodetector 6

from some minimum value of E

min to maximum E. Capacity condenser (kS

Cp decreases from some initial C to C,, "and the impedance increases from

 M Yip

Z0 to ZMt1H. Due to the nonlinear nature of the photo-emf of the photobag as a function of illumination (U InE), the output signal of the VDP phototransistor also non-linearly depends on the illumination and, therefore, on the displacement (Fig. 3). Connecting a shunt capacitor C0 to the MOS transistor's gate allows an increase in the photo-EMF of a photo battery with a decrease in its illumination, which achieves an expansion of the linear portion of the positional characteristics of the photodetector and an increase in the sensitivity of the sensor.

0

Claims (1)

Invention Formula A photoelectric pressure sensor, comprising a housing, a light guide, a light source and a force transmitting element, characterized in that in order to expand the measurement range and increase the sensitivity, it is equipped with a phototransistor made in the form of a metal-insulator-semiconductor field-effect transistor a battery of photocell elements is included, in the form of successively connected p - n junctions, and is also provided with a cantilever beam installed inside the body, the end of which is connected to the force transmitting element, and epodvizh and about / YYY-- with a metal plate mounted in a housing and parallel to the beam, while the phototransistor is installed opposite the end of the fiber that is attached to the console beam along the entire length. moreover, an electrical capacitance formed by a cantilever beam and a fixed metal plate is included in the phototransistor gate circuit. W dg them Thebes. 2 Fig.Z - &# & - $ Figm F. five Editor L.Pcholinsk Compiled by A. Zos mov Tehred L. Serdyukova Proofreader t.Papi Order 974 Circulation 462 VNI | IPI of the State Committee on Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk, 4/5  ace ei tt 6 Subscription