SU821960A1 - Temperature measuring device - Google Patents

Description

one

The invention relates to a technique for measuring temperature and may find application in measuring temperature under conditions of strong electromagnetic interference.

Temperature measuring devices are known that contain a source of a white matchmaker, a temperature-sensitive element with a temperature-dependent refractive index, and a recorder 1.

These devices have high noise immunity, but have a low measurement accuracy. .

Closest to the invention is a device for measuring temperature, which contains successively placed sources of monochromatic radiation, two crossed linear polarizers, between which are placed a heat-sensitive birefringent crystal, and a photodetector 2.

. The disadvantage of this device is the narrow range of measured temperatures.

The purpose of the invention is to expand the range of measured temperatures. .

The goal is achieved by the fact that in a device for measuring

temperature, containing sequentially placed source of monochromatic radiation, two crossed linear fields. An optical compensator of the phase difference installed between one of the polarizers and a double-refracting crystal, a narrow-band light filter installed in front of the photoreceiver, and a numerical indicator and a pulse array, and a frame, a set of counters, a set of counters, and a set of counters, are set up.

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Figure 1 shows a diagram of the device; 2 shows the nature of the dependence of the radiation intensity at the output of the device on temperature; in FIG. A graduation curve for a device with a birefringent plate of syngenite crystal.

The device for temperature measurement contains a source of monochromatic radiation, polarizers 2 and 3, sensor 4 (temperature-sensitive birefringent crystal), narrow-band light filter 5, photodetector b, counter 7 pulses, null indicator 8, capacitor 9 phase difference. The device operates as follows. A parallel monochromatic light flux from source 1 passes through a polarizer 2, a compensator 9, a crystal plate 4, a polarizer 3, then through a narrow-band light filter 5 hits the radiation receiver b. A thermally sensitive birefringent crystal, for which the initial minimum of the photocurrent is set , placed on the medium with the measured temperature, determine the increment of the phase difference transmitted through the temperature-sensitive element of the light wave when the compensation is set using ora minimum photocurrent and preliminary calibration coordinates in temperature - a difference F t Nachod target temperature environment; The increment of the phase difference, a multiple of 2k, is determined by the number of minima of the photocurrent, and the rest of it, the smaller, is determined by the difference in readings of the compensator corresponding to the initial and final minima of the photocurrent. The intensity of light I {t) recorded by the receiver can be represented, 2 V to 2, in the form of 3 5Ш S4n, n - - - ia, ili (where k can also be: a function of temperature t. It is clear that a set of photocurrent corresponds to perturut (mT + t), where, + 1, + 2 ..., T is characteristic of the chosen sensor (crystal, orientation of the sensor faces relative to the crystallophysical axes, sensor thickness) temperature interval, during the passage of which the light intensity changes in one period. In connection with these specified temperature range can be called the period of At k const, T4T (t), at (t), the temperature of T depends on temperature. The dependence T (t) is taken into account during calibration. In this respect, materials with phase transitions in the operating range, in the region of which As a rule, there are significant temperature anomalies, which complicate the calibration and the type of the calibration curve. In turn, such sharp anomalies can turn out to be useful when creating special purpose devices. The required environment temperature can be represented by such terms + wT + D + AL, where t is the initial device startup temperature (settings), which corresponds to and ha is the number of photocurrent minima recorded when the sensor temperature changes from the initial tg to the desired t; T is the sensor temperature period (corresponds to a phase that is a multiple of 2ft; & tiT is the temperature corresponding to the difference in the readings of the compensator set to the minimum of the photocurrent in the initial and final stages of measurement (corresponds to the phase less than 211) D - due to a change in the temperature of the sensor, the phase difference. The sensitivity of the proposed device for measuring temperature depends on the physical properties of the crystal used to make the sensor, the thickness of the sensor and the wavelength used When the period T is shorter, the sensitivity increases in accordance with the decrease in the division value of the compensator graded in temperature units; / N, where T is the temperature period, the number of compensator divisions corresponds to a phase change of 2lt (period T). In the simplest case ( t), where it is taken into account that for most materials ./.. ,, 91 Thus, it follows from formula (2) that crystals with a large temperature dependence of birefringence should be used as a temperature-sensitive element, and for illumination the source for emitting at short wavelength capabilities. The period T can be reduced by increasing the thickness of the temperature-sensitive element, however, this increases the thermal inertia of the sensor and undesirable temperature gradients. With small thicknesses of sensors, their effective thickness can be increased by repeated passage of the beam in the crystal plate. When using a Berek compensator, it is possible to measure the phase difference to 0.01 band, so that the accuracy of the temperature measurement is 0.01 T. Example. The sensor is made of syngenite crystal. It has a fortuy rectangular plane-parallel plate measuring 10x10x0.5 mm, cut out perpendicularly sharp

bisector of the optical indicatrix of the crystal. Large surfaces of the cris-i plate of the tall plate are polished. An LG-56 laser (, 8 nm) was used as a radiation source. The photocell F5 served as a radiation receiver; a standard pulse counter and Berek compensator were used. When calibrating the device, a crisscale plate was placed in a heat chamber, the temperature of which was controlled by a thermocouple. The calibration results are shown in FIG. 3, from which it can be seen that for the sensor in question (syngenite) the phase difference varies linearly with temperature, so the period T does not depend on temperature.

At high temperatures, when the intensity of luminescence of the object being studied becomes, a narrow-band filter should be placed along the rays, transmitting only the radiation of the applied radiation source. This will reduce the overall photocurrent and improve the contrast of the interference pattern.

Thus, the proposed device allows the temperature to be measured in a much wider range.

Claims (2)

1. USSR author's certificate 5 No. 590617, cl. G 01 K 11/12, 1976. 2. For Japan 48-13477 IIIE8, published 1973 (prototype). 3, rel. ed .1 200 tC