SU1578513A1 - Device for measuring temperature - Google Patents

Abstract

The invention relates to temperature measurements and makes it possible to increase the measurement accuracy by reducing the progressive error of a thermoelectric converter (TEC). An alternating current from the converter 14 is passed through the junction of TEC 1, the voltage being connected to the output of the source 13 of the reference voltage. The signal from TEC 1 through the amplifier 2 modulator-demodulator is fed to the first input of the first differential amplifier 4, the second input of which receives a signal from the output of the controlled source 3 of the reference voltage. From the output of the differential amplifier 4, the signal is fed through the high-pass filter 6 to the input of the phase-sensitive rectifier (PSF) 8, and through the low-pass filter 5 to the input of the second differential amplifier 7, to the output of which the recorder 10 is connected. the output signal of the FWC 8 and the voltage divider 12. Compensation of the error is carried out by comparing a part of the reference voltage removed from the 12 voltage divider with the amplitude of the increment of the thermopower of TEC 1 due to the Peltier effect when the alternating current passes through the ACI junction 1. 1 Il.

Description

The invention relates to temperature measurements and can be used to measure the temperature of various media and objects.

The purpose of the invention is to improve the accuracy of temperature measurement by; reducing the progressive error of the thermoelectric converter.

The drawing shows a diagram of the proposed device.

The device contains a thermoelectric converter (TEC) 1, an amplifier 2 modulator-demodulator (UMD), a controlled source 3 reference voltage, a differential amplifier 4, a filter (LPF) 5 low frequency, a filter (HPF) 6 high frequency, the first differential amplifier 7, phase-sensitive rectifier (FV)

8, the second differential amplifier

9, the recorder 10, the switch 11, the voltage divider 12, the reference voltage source 13, the voltage-current converter 14 (PNT) and the control unit 15.

U1 1

eo

: l

:about

The device works as follows.

Under the influence of temperature $ of the controlled medium at the outlet of TP i, thermopower is generated:

1, - 8.0, + 1

x

(ABOUT

3 reference voltages;

U in - the voltage at the output of the differential amplifier 9 o

At the output of the low-frequency filter 5, a voltage is formed equal to

where S, A + 2B0, + ZSb is the sensitivity, TP of the TP at the operating point at temperature b,; A, B and C are constant coefficients depending on the material of the TP electrodes; thermopower value of free ends of TP.15

When the switch 11, controlled from block 15, is closed, the current from the voltage-current converter 14, which is a current generator, flows through the junction of TP 1. At the same time, the TP junction is positively heated (cooled) depending on the direction of the current flowing through the junction, in proportion to the amount of electricity passed through it due to the 25 Peltier effect, and the thermopower TP value becomes equal to

12 .iu QVn sz (Qft K,: J) + V

(2) 30

where S2 is the sensitivity of the TP at a temperature of 9g 9 | ± & b - additional temperature

heating (cooling) the spa; 35 K - current-to-spa temperature conversion ratio When the switch 11 is operated with a frequency of $ 2 from the thermo-ECU control unit 15, TP 1 will pulsate 40 along a rectangular envelope. The amplified DMD 2 thermoEMF is transmitted to one of the inputs of the differential amplifier 4, to the other input of which the voltage is supplied from the output of the controlled source 3 of the reference voltage 0 When the switch 11 key is open and closed, the voltage of the differential amplifier 4 is respectively generated equal to 50

and; K4 (Ktl, - K5U,);

uj - VKZV k3i,),

(3)

where K2 - gain factors

amplifiers 4 and 2; Kj - controlled source transfer coefficient

..-..-.

(four)

where KS is the transmission coefficient of the low-pass filter 5U. If conditions are met, b and SiscS1 equation (4) can be represented as

U5 (8,0,4-1- S, K, I + + 1 „) - K3U,. (5)

The variable component of the pulsating voltage is extracted by the high frequency filter b and is rectified by the phase-sensitive rectifier 8, controlled by the control unit 15 The rectified voltage is

ia - k8.kb

yll-ui- 1 k - K –K x 2 2864x

XK2. S. K, 1;

(6)

where K, and K8 are respectively the conversion factors of the HPF 6 and the HPF 8 "In the differential amplifier 7, the output voltage of the HPF 8 is subtracted from the output voltage of the LPF 5, the amplified voltage difference is recorded by the recorder 10, When the conditions Kj Kg-K6 and Kr1x K -jUg, which is achieved when the condition is met

". u v h - --- 1g,

k5 s, - K, K ()

(7)

the signal U7 at the output of the differential amplifier 7 will be determined by the expression

(eight)

U,. 2KILK 7. KH KI where K7 is the gain of the differential amplifier 7;

K1g is the division factor of the voltage divider 12;

Claims (2)

SUMMARY OF THE INVENTION A device for measuring temperature, comprising a thermoelectric converter, a control unit, the first output of which is connected to a control input of a switch, a reference voltage source and a recorder, characterized in that, in order to increase the measurement accuracy, three differential amplifiers are introduced into it, an amplifier modulator - demodulator, controlled reference voltage source, high-pass filter, low-pass filter, phase-sensitive rectifier, voltage divider and converter voltage-current, the input of which is connected to the first output of the reference voltage source, and the output through the switch is connected to thermoelectric 3 6 with a transducer connected to the input of the amplifier, the modulator - demodu-. an amplifier whose output is connected to the first input of the first differential amplifier, the second input of which is connected to the output of a controlled source of reference voltage, and the output is connected to the inputs of a high-pass filter and a low-pass filter, the outputs of which are connected respectively to the input of a phase-sensitive rectifier and the first input of the second differential amplifier , the output of which is 15 RSGO connected to the registrar, and the second input is connected to the output of the phase-sensitive rectifier and the first input of the third differential amplifier rer, the second input of which the voltage across deli20 Tel is connected to the second output of the reference voltage source and an output connected to the control input of a controlled source of reference voltage, wherein the input-governing uprav25 phase-sensitive rectifier is connected to the second output of the control unit.