SU1425483A1 - Optical pressure transducer - Google Patents

Abstract

The invention relates to a measurement technique and makes it possible to increase the accuracy of pressure measurement. Laser beam source 1, passed through a quarter. wave plates 2-4, the polarizer 5 and the sensitive element 7, are directed by the beam-splitting mirror 8 in two directions: directly to the photodetector 10 of the reference channel and through the polarizer 6 to the photodetector 9 of the measuring channel, the signals from which are fed to the amplifier 11 of the signal difference . A change in the t-ry of the sensing element 7 causes a change in the signal of the thermocouple 14 through the amplifier 15 to the reversible electric motor 13. Rotation of the polarizer 5 connected to the electric motor 13 in the appropriate direction ensures that the intensity of the light falling on the photodetector 9 remains constant. 1 Il.

Description

12

(L

with

four

Is:

ate

wasp

OS

 The invention relates to pressure transducers based on the polarization-optical method for determining voltage.

The purpose of the invention is to improve the accuracy of pressure measurement;

The drawing is a schematic diagram of an optical pressure sensor.

The sensor contains a laser radiation source 1 quarter-wave plates 2-4, polarizers 5 and 6, a birefringent sensing element 7, a beam-distributing mirror 8, photodetectors 9 and 10, an amplifier 11 of the difference of signals, reversible electric motors 12 and 13, a thermocouple 14 and a differentiation circuit amplifier 15c.

The polarization-optical system makes it possible to measure pressure by rotating one of the polarizers, such as an analyzer, to compensate for changes in the intensity of light I due to the effect of pressure on the sensing element. By rotating the polarizer, it is possible to compensate for changes in the intensity I due to a change in the temperature of the sensitive element. As a result, pressure accuracy is significantly improved.

The sensor works as follows.

The beam from the laser radiation source 1 passes a polarization-optical system consisting of quarter-wave plates 2–4, a polarizer 5 and a sensing element 7 is divided by a light-transmitting mirror 8 into two beams, one of which passes through a polarizer 6 onto the photodetector 9 measuring channel, and; the other is on the photodetector 10 of the reference channel. The pressure difference induced by pressure P in the 4yBCTBHTevTb element 7 leads to the appearance of virness between the photoelectric signals from photoreceivers 9 and 10 to the amplifier 11 of the difference of signals. The latter drives a reversing motor 12, which pushes analyzer 6 by an angle of yes towards the equation for the values of photosignals in both channels. The pressure is determined by the value of Da. For the initial setting of the operating point of the device, a variable resistance R is used in the linear portion of the intensity dependence I.

When the temperature of the sensing element 7 changes, the difference in stroke in the latter and, accordingly, the intensity of the light falling on the photodetector changes.

9, with the result that a difference in photoelectric signals from photodetectors 9 and 10 appears. This is in the absence of a device for compensating for temperature

a change in the path difference in the sensing element 7 causes the polarizer 6 to rotate at a certain angle, programmed in units of pressure, and, accordingly, to an increase in the error of pressure measurement. In the presence of such

 The device simultaneously with the temperature change of the sensing element 7 changes the thermoelectric signal of the thermocouple 14 in contact with the sensing element 7. This signal amplifies5 with the amplifier 15 and is fed to a reversible electric motor 13. The latter rotates the polarizer 5 in the direction corresponding to compensating for temperature variations in the intensity of light I, falling on the photodetector 9, due to

0, the temperature changes of the difference in travel in the sensing element 7. Therefore, with a change in temperature, the intensity of the light falling on the photodetector 9 does not change, respectively, does not deteriorate

2 and a predetermined accuracy of determining pressure P, due to the piezo-optical sensitivity of the birefringent element 7. In the proposed sensor, the accuracy of pressure determination is improved by eliminating the parasitic effect of temperature changes of the birefringent sensing element.

Claims (1)

Invention Formula An optical pressure sensor containing a laser radiation source, two 5 quarter-wave plates and a birefringent sensing element mounted between them, a beam-splitting mirror, a polaroid analyzer and a feedback circuit containing photodetectors of the reference and measuring channels connected via an amplifier to a reversible electric motor connected to a polaroid analyzer, distinguished by that, in order to improve the accuracy of pressure measurement, an additional quarter-wave plate and a polarizer installed after the radiation source were inserted into it, as well as installed Sola- tion to compensate for temperature changes in the path difference in the sensitive element, consisting of successively connected thermocouples mounted on the sensitive element, an amplifier with a differentiating circuit and a reversible electric motor connected to a polarizer.