SU666444A1 - Temperature-measuring device - Google Patents

Description

I

The invention relates to temperature measurements, namely, devices for measuring temperature with correction of a calibration characteristic.

A device for measuring temperature d} is known, which contains a thermoelectric thermometer and a correction device connected to the inputs of the adder, the output of which is connected to the measuring device. In this device, periodic compensation of the temporal drift of the calibration characteristic of a thermoelectric thermometer is carried out according to the results of calibration.

However, the known device is characterized by an insufficient accuracy of correction, moreover, it requires the dismounting of the thermometer and additional equipment during calibration.

A device is known comprising a thermoelectric thermometer, a measuring instrument, a calibrator with a reference material, and a power source for the heater of the 2J calibrator. This device

allows to check the thermometer, determine the drift of the calibration characteristic.

The closest to the invention in its technical essence and the effect achieved is a temperature measuring device containing a thermoelectric thermometer equipped with a calibrator, connected to the control unit 1, a measuring instrument, an adder, the first input of which is connected to the correction block of the additive error component, and the output connected through the switch with the measuring instrument; rum and the first input of the comparison unit, the source of the reference voltage L3J.

This device provides not only verification of the primary converter at the place of operation, but also automatic correction of the error, which increases the measurement accuracy.

But such a device does not completely compensate for the error of a thermoelectric thermometer in a wide range of measurements, but only at one temperature value — at the phase transition point of the calibrator material. As the measurement error increases from this point, the measurement error will increase, and if the sign of the error of the thermoelectric thermometer changes, the measurement error may turn out to be even larger than before the introduction of the correction. The purpose of the invention is to improve the measurement accuracy of a wide temperature range. The delivered circuit is achieved by introducing a multiplier correction component into the temperature measuring device, a second adder, the inputs of which are connected to a multiplicative component correcting unit and a thermoelectric thermometer, and the output connected to the second input of the first adder, the second source the nickname of the reference voltage, the second switch, the inputs of which are connected to the sources of the reference voltage, and the output to the second input of the comparator unit, the output of the comparator unit connected to the third They are connected by a switch, the outputs of which are connected to correction units, and the outputs of the control unit are connected to the control inputs of the switches and the control input of the correction unit of the multiplicate error component. Fig. 1 shows a block diagram of the device in Fig. 2, graphs explaining the operation of the device. Curve A depicts the dependence of the thermoelectric thermometer's temperature on temperature, Direct B shows the corrective EMF on temperature. The device contains a thermoelectric thermometer 1 equipped with a calibrator, an adder 2, a correction multiplier 3 unit of the error component Thermo thermometer, a control unit 4, switches 5, 6, 7, an additive component correction unit 8 of a thermometer error, an adder 9, a measuring instrument 10, a comparison unit 11, reference sources 12, 13. The device operates as follows. Before measurements, a thermoelectric thermometer installed on the object is calibrated. The object is transferred to the constant heating mode, the control unit is switched on for operation in the calibration mode. 44 B1,1 the input signal of the thermometer 1 through the adders 2 and 9 is fed to the measuring device 10, while the output signals of the blocks 3 and 8 of the correction are equal to zero. At the time of the phase transition of the reference material at temperature t .. the output signal of thermometer 1 becomes constant, and control unit 4 issues a command to switch 5 to switch the output signal of adder 9 from input of measuring device 10 to input of comparator unit 11 Output signal of adder 9 compares with The standard emf corresponding to the temperature b, which comes from the source 12 through the switch 7. The output signal of the comparison unit 11 through the switch 6 is fed to the control input of the correction block 8 additive is $ error output signal which begins to be varied until the difference between the output signals of the adder 9 and the standard signal source 12 is less than threshold comparing unit 11. After completion of the phase transition process of the calibrator reference material, the control unit 4 disconnects the outputs of the adder 9 and the source 12 from the inputs of the comparison unit 11. In this case, the error of the thermoelectric thermometer 1 at the beginning of the measurement range, which is the additive error component, is corrected. Upon reaching the phase transition temperature of the second reference material at a temperature: t2 {at the end of the measurement range), at the command of the control unit 4, the comparison inputs of the comparison unit 11 are connected to the outputs of the adder 9 and the source 13, the output signal of which corresponds to the standard EMF value at a temperature of 2 Output signal of the unit 11 through the switch 6 is fed to the control input of the correction unit 3 of the multiplicative component of the thermometer error. The output signal of this block is proportional to the measured temperature, which is ensured by the presence of a connection between the control block and one of the control inputs of the correction block of the multiplicative component. This relationship is linear. Under the action of the output signal of the comparator unit 11, the slope of this proportionality is set at the time of calibration at temperature tj. Until the

This coefficient was equal to zero, and the output signal of block 3 was absent.

In the Measurement mode, the input EMU of the thermometer with the EMF receives a correction EMF from correction blocks 3, 8, which changes with temperature and almost completely compensates for the error of the thermometer in a wide temperature range.

Only the component of the error remains uncompensated, which is associated with the discrepancy between the shape of the error curve (curve A) and the dependence of the correction emf on temperature (direct B), but it is insignificant.

The calibrator, built into the protective cover of the thermometer 1, consists of two small volumes of pure metal in a graphite shell, which has good thermal contact with the hot weld of the thermometer.

The additive error correction block 8 can be performed, for example, on the basis of a bridge fed from a reference voltage source.

One of the shoulders of the bridge includes a calibrated reohord with a controlled drive. The input of the correction unit 8 is the control winding of the reichord drive, and the output is the unbalance voltage of the bridge.

The multiplicative component error correction block 3 can be made on the basis of a bridge, a source of reference voltage, and two rheochords with independent control drives. One rheochord is included in the power supply chain of the bridge, the second one into one of its shoulders. The control inputs of block 3 are the control winding inputs of the drives, and the output of the block is the voltage unbalance of the bridge. The slider of the rheochord included in the power supply circuit of the bridge should move in proportion to the temperature, and the control winding of the second rheochord drive receives the output signal of the comparator unit 11 at the time of calibration at a temperature of 2- The calibration balance at temperature t2 is in balance and its output voltage zero, although its voltage increases with the temperature of the atura. At the time of calibration, the voltage of the bridge unbalance increases until the output signal of the adder 9 is comparable to the standard DPS value corresponding to the phase transition temperature of the calibrator reference material at temperature t The control unit 4 circuit must contain a differentiator for fixation; moments of phase transitions of the calibrator materials, at which the derivative of the output signal of the thermometer is zero, and also a device for generating a drive control signal of the unit 3 for moving the slider of one of its railways is proportional to temperature.

The proposed device provides automatic correction of the time drift of the thermodynamic characteristic of the thermoelectric thermometer.

Since the phase of the input signals of the correction blocks can independently vary, the device provides compensation for 0 time drift and the initial spread of the calibration characteristics of thermoelectric thermometers with any law of variation of the error, including when changing the sign of the error

5 in different parts of the measuring range.

During operation of the device, there is practically no need for preliminary and periodic verification of thermoelectric thermometers, since compensation of the error occurs in the entire measurement range. This simplifies and reduces the cost of metrological support of production, and also allows for the expansion of

Scope of application of the device.

Claims (3)

1. Sachenko A. A., Kochan V. A. Improving the accuracy of temperature measurement using thermoelectric thermometers. Measuring equipment, 9, 1974, p. 51. 2. USSR author's certificate NO 339SO6, cl. K 7 / O2, 1§70. 3. USSR author's certificate number 569876, class; Q O1 K 7 / O2, G 01 K 15 / OO, 1976. Si le fui.2