SU1737280A1 - Temperature measuring device - Google Patents

Abstract

The invention is intended to measure ambient temperature. The aim of the invention is to increase the resolution of the device. The device contains a resistive temperature sensor and a transducer of the value of temperature to frequency. The electroacoustic transducer introduced delay line 4, is included between the output of the controlled multivibrator 3 and the input of the amplifier 5 connected with the output control input of monostable multivibrator 2. Yield monostable multivibrator 2 is connected to a control input controlled multivibrator 3. Said elements form highly stable ring electroacoustic whose cyclic frequency is controlled by a thermistor that serves as a temperature sensor. 1 il. (L

Description

The invention relates to a measurement technique and can be used in the development of instruments for measuring ambient temperature.

A temperature meter is known, the sensor of which serves as a control element of a multivibrator - an oscillator {jJ. The change in the frequency of the oscillator is proportional to the change in temperature.

As a prototype, a temperature-frequency converter containing a thermistor and a CMOS multivibrator} lj is taken. In this temperature meter, the sensor also controls the frequency of the oscillator based on the multivibrator.

The disadvantage of the meter, adopted for the prototype, as well as other devices of this type is the low measurement resolution due to the own unstable frequency of the generator included in its composition. As it is known, the stability of the frequency Af / f, the ratio of the frequency deviation uf from the average value of f with the parameters of the environment and the circuit unchanged, for harmonic oscillators on RC - (R is the electrical resistance, C is the capacitance of the capacitor) does not exceed 10 - 10, and for generators on an LC circuit, pax (L is the inductance of the circuit) does not exceed 1 ((G V high quality pulse generators, this value can reach 3 10, which corresponds to a conversion error of 0.03%.

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Thus, in the known measures of physical parameters, measurements are not provided with an error less than 0.1-0.03% of the measured value.

The aim of the invention is to improve the measurement accuracy.

The goal is achieved in that a temperature measuring device containing a standby multivibrator, made with a thermistor in its control circuit and connected by an output to the control input of a controlled multivibrator, and an amplifier connected by an output to the output bus, is provided with an electroacoustic delay line, form of piezoelectric transducers and placed

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between them is a tube filled with water-1 glycerin mixture.

The above units of the device, connected in a ring, form a pulse-cyclic generator controlled by a temperature sensor. The stability of the electro-acoustic delay line is very high and reaches a value. The inclusion of a tunable delay device in an electroacoustic ring circuit allows it to be started with highly stable pulses, and the cut of a highly stable pulse determines the high initial accuracy of the tunable delay device. Since the multivibrator is standby, the frequency stability of the converter maintains the required high level. The pulse is reset by the measured parameter: temperature.

According to available information, pulse generators, electroacoustic delay lines and tunable delay devices have not been used previously to increase the resolution of physical parameter meters.

The drawing shows a block diagram of the proposed device for measuring temperature.

The sensor of the device is the thermistor 1, which is included in the control circuit of the waiting multivibrator 2. The electro-acoustic ring includes a generator 35 of 3 pulses, a delay line and

amplifier 5. The pulse generator is a multivibrator whose natural frequency is slightly below the operating frequency range of the meter. The delay line contains a sealed tubular body 6, which is closed at both ends by piezoceramic transducers 7 and 8. The body is filled with a water-glycerin mixture, the sound speed in which varies minimally from temperature fluctuations of the environment. The length of the acoustic element and the characteristic Q of the thermistor 1 are chosen such that the delay in the acoustic element exceeds the maximum delay in the waiting multivibrator 2. The electro-acoustic ring is provided with a tap 9 for picking up frequency signals.

The device works as follows. Radiating transducer 7, excited by generator 3, send30

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em in the acoustic element sound pulse. This sound impulse reaches the receiving transducer 8 and is transformed into an electrical impulse. Amplified by the amplifier 5. The delay on the acoustic element of the delay line k is constant and has a high stability index. A shearing multivibrator 2 is triggered by an electrical pulse from amplifier 5. By the falling edge of the multivibrating standby pulse, the duration of which is determined by the state of thermistor 1, the pulse generator 3 starts again and a new cycle starts. Thus, the total cycle time is controlled by the thermistor 1, as a result of which the frequency of the electrical oscillations in the electroacoustic ring is removed at 9 proportional to the value of the measured temperature. The peculiarity of the pulse-cycle temperature meter is that, due to the repeated passage of pulses through the waiting multivibrator, a statistical averaging of the spread of the values of its delay time occurs. Such averaging of the scatter

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The proposed design of a temperature measuring device is stable, which is at least two orders of magnitude higher than that of the prototype. The simplicity and small size of the structure make it possible to create convenient and highly accurate physical instruments that have a lower cost than existing ones.

Claims (1)

A device for measuring temperature, comprising a standby multivibrator made with a thermistor in its control circuit and connected by an output to a control input of a controlled multivibrator, and an amplifier connected by an output to an output bus, characterized in that, in order to improve the measurement accuracy, An electro-acoustic delay line is inserted in it, connected between the output of the controlled multivibrator and the input of an amplifier connected to the control input of the waiting multivibrator, The acoustic delay line is made in the form of piezoceramic transducers and permits even more improvement in the accuracy of the 30 tube placed between them, the completed measurements, and the water-glycerin mixture. five 0 five 0 five The proposed design of a temperature measuring device is stable, which is at least two orders of magnitude higher than that of the prototype. The simplicity and small size of the structure allow the creation of convenient and high-precision physical instruments that have a lower cost than the existing ones. A device for measuring temperature, comprising a standby multivibrator made with a thermistor in its control circuit and connected by an output to a control input of a controlled multivibrator, and an amplifier connected by an output to an output bus, characterized in that, in order to improve the measurement accuracy, An electro-acoustic delay line is inserted in it, connected between the output of the controlled multivibrator and the input of an amplifier connected to the control input of the waiting multivibrator, oakustiches. The delay line is made in the form of piezoceramic transducers and