SU1000789A1 - Device for remote measuring of temperature - Google Patents

Description

The invention relates to a measurement technique, namely, devices for remote temperature measurement. It can be used in the systems of accurate measurement and automatic temperature control at hard-to-reach, remote and severely operating facilities. V A device for temperature measurement is known, which contains a PA sensing element based on surface acoustic waves,: connected to a radio frequency generator circuit installed at the measurement object.

The disadvantage of such a device is the limited range of measurements of the temperature, which is determined using semiconductor elements in the generator circuit.

The closest in technical essence and achievement of the result of the invention is a device for measuring temperature, containing a passive re-teacher with a delay line on surface acoustic waves as a temperature-sensitive element, a transmitter and receiver of oadipulses and a recorder L 2.

The disadvantage of this device is the low accuracy of the measurements. neither is the impossibility of direct use for automatic control of the temperature of objects. The latter is due to the monotonous nature of the time dependence.

10 line delays on surface acoustic waves on temperature.

The purpose of the invention is to improve the accuracy of temperature measurement and the expansion of functional capabilities

15 devices.

The goal is achieved through the following: -WPT in a device for remote temperature measurement, containing a passive re-radiator

20 with a draw line on surface acoustic waves as ter- element, transmitter and receiver of radio pulses and. The recorder, a part of the passive re-radiator, was introduced, an additional line of the trigger on the surface of acoustic waves, with both delay lines connected in parallel and of opposite sign.

30 temperature delay coefficients, and the radio pulse receiver contains a synchronous detector and a low-pass filter connected in series to the recorder's input. The recorder is designed as a half-period counter of the amplitude envelope of received radio pulses. The drawing shows the electrical circuit of the device. The device contains a passive: a transducer mounted on the measurement object 1 and includes a temperature-sensitive element 2, an antenna 3, a transmitter 4 and a receiver 5 operating on one common antenna b, a recorder 7. The temperature-sensitive element 2 is a piezoelectric substrate (for example, niobate lithium, quartz), on the surface of which two delay lines of surface acoustic waves are formed. The kan from the LINE delay is formed by two counter-pin surface wave transducers (8 and 9 for the first delay line; 10 and 11 for the second) and a sound guide as a surface layer of the substrate between the transducers (12 for the first delay line and 13 - for the second). The drivers 8 and 9, 10 and 11 are oriented on the substrate surface so that the surface acoustic waves in the first and second delay lines propagate along the X axis and the corresponding opposite values of the temperature coefficients of the delay equal in magnitude and opposite in sign. Transducers 8-11 are electrically connected in parallel and connected to the antenna. Transmitter 4 contains a stable high frequency generator 14, an impulse generator 15, a delay line 16, a modulator 17 and a standby multivibrator 18. Receiver 5. Contains an electronic switch 19, a synchronous detector 20, a filter 21 low frequencies, a phase shifter 22. The device operates as follows. High-frequency radio pulses produced by transmitter 4, having a repetition period of tT and a duration. Tc,, are radiated by antenna b in the direction of the antenna 3 of the passive re-radiator and then received by antenna 3, the transformer sh 8-11 transforms into surface acoustic waves (acoustic impulses) and propagates in the sound ducts 12 and 13 of the first and second delay lines over two pairs of encounters directions (wavy arrows) Surface acoustic waves delayed in the 12-by-13 ducts are transformed by converters 8-11 into radio pulses that are bitches; they are combined in phase relationships depending on the substrate temperature. or are luminant with it in thermal contact with the measurement object. The total pulsed radio signals are reradiated by antenna 3 in the direction of antenna b, received by antenna b and fed to receiver 5. The complex transfer coefficients of the first and second delay lines in the case of a linear dependence of their delay times on temperature, equal in magnitude and opposite in sign temperature coefficients of delay and the insertion loss can be represented as i (, - KoexpH2-icfToti-fol.r (tt;); (d) The pH of the pH is 2 Gs m „1- (G-1o) (2) where K is the modulus of the transfer coefficient ° delay lines; j - imaginary unit; f g frequency, Hz; - time in holding lines at an appropriate temperature L, which is equal to the delay times of the first and second lines as functions of temperature, s; s (.- p is the absolute value of the temperature coefficient of delay of the lines, o current temperature, s. Based on the superposition principle, the complex transfer coefficient of the temperature-sensitive element 2 up to a constant set depending on the conditions of matching the temperature-sensitive element with antenna 3, taking into account (1) and (2), it can be represented as -Koco5i: iirfTofll-rCt ° -t;) JexpC-J2-fE {To). a) In order to obtain the superposition of the responses of the first and second delay lines, their duration must be significantly longer than the maximum change in the delay time of the lines in the measured temperature range D In this case, the amplitude of the 3 radio pulses re-emitted by the antenna depends on the cosine law, as follows from the expression (3 ). The zero value of the amplitude of reradiated rad pulses corresponds to the antiphase value of the transmission coefficients of the first and second delay lines. The temperature interval & t between its lv; m adjacent ypoBHHNM t and. Corresponding to zero voltage — amplitudes of re-emitted radio pulses, is determined from the expression (3): where is the number of acoustic wavelengths placed in the acoustic conductor of the first or second delay line at temperature t . The value of n in the lines of the surface acoustic wave can reach with acceptable losses of no more than 40 dB / 10 -10, and the order for the most heat-sensitive materials, such as niobate lithium, reaches Hence, on the basis of formula (k) it follows that It can be obtained as O, 1-1,. Then the accuracy of measuring the small deviation of temperature from the levels, corresponding to a zero value of the amplitude of the re-emitted radio pulses, can reach 0.01-0. Radio transmitter pulses are generated by modulating the high-frequency signal of generator 14, delayed in delay line 16 at time T) by generator pulses 15. It is carried out in modulator 17. Holding T is necessary to lock the receiver until the transmitter starts each pulse. The receiver is locked by means of an electronic switch 19, triggered by the pulses of the waiting multivibrator 18, which closes the transmitter pulses in time. The standby multivibrator is triggered by the leading edge of each pulse of the generator 15. Radio pulses received by the antenna 6, passing through the electronic switch, are fed to one of the inputs of the synchronous detector 20. The other input of the synchronous detector passes through the phase shifter 22 the generator 14. phases of the high-frequency filling of received radio pulses and the signal of the generator 14, which are fed to the inputs of the synchronous detector 20. The carrier frequency of the radio pulse may be selected in the range of 10 1000MHz, which can vats uses the delay line surface acoustic waves. The choice is determined by the characteristics of the radio channel, its length, the design requirements and the dimensions of the antennas 3 and 6. The envelope amplitudes of the received radio pulses, which carries information about the temperature of the measurement object 1, are separated from the spectrum of the output signal of the synchronous detector 20 and supplied to the recorder 7. To measure the temperature, which varies widely (as opposed to its small change from one of the levels), or to determine the level number, the recorder 7 can be made as a counter, fixed iruyuschego number of periods or half-periods oshbayuschey amplitudes of the received RF pulse that is proportional to temperature of the object or number of levels. The thermal element must be protected from aggressive media by placing it in an evacuated body (not shown). Thermal contact with the object of measurement can be made through the wall of the housing or through infrared radiation of the object. In the latter case, the body must be transparent (for example, from quartz glass). The design of the temperature-sensitive element may differ from that described above. The first and second lines of delay can be made on two substrates of different piezoelectrics. The substrate may be non-piezoelectric, for example, of fused quartz. In this case, delay lines are made on the basis of piezoelectric films, for example aluminum nitride, capable of operating at temperatures up to 1000 °. Transmitter 4 may contain a power amplifier, including on-output at the output of the modulator 17, and receiver — a direct current amplifier at the output of the low-pass filter 21. The input circuit can also be entered into the receiver 5. A high frequency amplifier between the switch 19 and the synchronous detector 20 can be input. With a high level of interference and high attenuation of radio signals and a temperature-sensitive element 2, the presence of these devices in the transmitting-receiving part becomes necessary. Using the device, it is possible to measure the temperature of objects from a cryogenic one, where the parameters of devices on surface acoustic waves are even higher than during normal. (20 C), up to several hundred degrees when using such common piezoelectrics as niobate lithium and quartz. The upper limit can be increased by applying more heat-resistant piezoelectrics. The proposed device provides high accuracy of remote measurement and temperature control. It is easily miniaturized, technologically advanced and has a high reproducibility of parameters characteristic of devices using surface acoustic waves.

Claims (2)

Claim 1, A device for remote temperature measurement, comprising a passive re-emitter with a delay line on surface acoustic waves as a temperature-sensitive element, a transmitter and receiver of radio pulses, and a recorder, characterized in that, in order to increase the accuracy of temperature measurement and enhance functionality,. An additional delay line on surface acoustic waves was added to the passive re-emitter, with both delay lines connected in parallel and with opposite signs of temperature delay coefficients, and the radio pulse receiver contains a synchronous detector and a low-pass filter connected in series to the recorder input, 2. The device according to nil, characterized in that the recorder is designed as a counter of the number of half-periods of the envelope of the amplitudes of the received radio pulses. Sources of information taken into account in the examination 1.Patent of France 2423762, cl. G 01 K 11/22, published. 04.20.78. 2. USSR author's certificate No. 923263, cl. G 01 K 11/22, 10.16.80 (prototype).