SU1747952A2 - Device for determining time constant of thermal pickups - Google Patents

Abstract

SUMMARY OF THE INVENTION: The device comprises a sensor 1 under test, an exemplary thermal sensor 2, a subtraction unit 3, an integral-differentiation unit 4, a voltage autocompensator 5, a measuring and conversion unit b, an adder 7, a voltage setting device 8, a measuring unit 9, two zeroes authority 13 and 14, the element And 15, the switch 16, the inverter 17, 1 Il.

Description

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The invention relates to thermometry and is an improvement of the invention according to the auth st. No. 1642273.

A device for determining the time constant of temperature sensors is known, comprising an exemplary temperature sensor, a subtraction unit, an integro-differentiating unit, a voltage compensator, a voltage setting unit, an adder, and a measuring unit that are in functional relationship

A disadvantage of the known device is the necessity of adjusting it before each measurement, by discarding the polarities of the output signals of the subtraction unit and the integro-differentiating unit, as well as setting the appropriate polarity of the voltage supplying the measuring-transforming unit. As a result, the measurement accuracy of the post sensor time is reduced.

Indeed, in order for the autocompensator to operate normally, the inputs to its inputs must receive in-phase signals. At the same time, the polarity of the signal at the output of the subtraction unit depends on the ratio of the known time constant To and the measured time constant TL

At the same time, it is necessary to set the appropriate polarity of the supply voltage of the measuring and transforming unit, at the output of which a signal is formed that is proportional to the difference of the time constants of the sample and the temperature sensors under study. Obviously, the polarity of this signal must also correspond to the ratio of To and P.

The purpose of the invention is to improve the accuracy of determining the constant time of a thermal sensor by eliminating the need to match the polarities of the output signals of the subtraction unit and the integrating-differentiating unit, as well as setting the corresponding polarity of the voltage supplying the measuring-transforming unit.

To achieve this goal, a device containing two thermal sensors, outputs connected to the corresponding inputs of the subtraction unit, serially connected integrative differentiating unit with adjustable transfer coefficient for the derivative, automatic voltage compensator, measuring and transforming unit and voltage setting device, output connected to the second the input of the adder, and the second input of the subtraction unit is connected to the input of the integro-differentiating unit, regulating

the input of which is connected to the output of the voltage compensator; the first and second null organs, the I element, the inverter and the switch with two switching elements are additionally introduced, and the output of the integro-differentiating block is connected to the first input of the I element and the block output subtraction through the second null-organ is connected to the second

0 input element And through the normally closed contacts of the first switching element of the switch and the inverter to the second input of the voltage compensator and to the normally open contacts of the first

5 of the switching element of the switch connected by the control input to the output of the element I, and the power terminals of the positive and negative polarity of the measuring and transforming unit are connected to its first output respectively via the normally closed and normally open contacts of the second switching element of the switch. The drawing shows the structural scheme of the device.

The device for determining the time constant of thermal sensors contains test 1 and exemplary 2 thermal sensors, a subtraction block, an integral-differentiating block 4 with an adjustable derivative over the derivative, a voltage auto-compensator 5, a measuring-converting block b, an adder 7, a unit 8 of voltage, measuring unit 9, element 10 of comparison, amplifier 11 and actuator 12 of autocompensator 5 voltage, first 13 and second 14 zero-organs, element 15, switch 16c with two switching elements and an inverter

0 17 analog signal.

The device works as follows.

When thermal sensors 1 and 2 of the same non-stationary perturbation5 of arbitrary shape are applied, the outputs of blocks 3 and 4 appear identical in shape, which, depending on the ratio of the constant times of sensors 1 and 2, can be either in phase or Against the phase. In the first case, the action of the output signal of the element 15 triggers the switch 16. At the same time, the output signal of the subtraction unit 3 is fed to the input of the voltage compensator 5, the mine inverter 17, and the power terminal of the unit 6 is supplied with a voltage of such polarity as ( the signal is inverted by block 4) the generated output signal of block 6 corresponded to the difference (To-Ti), ja is negative

positive voltage at the output of the sensor 8..

In the second case, the switch does not work, the output signal of block 3 is inverted, and the polarity of the signal at the output of block b is set to the corresponding difference (TmTo), namely positive with a positive signal at the output of block 8,

Otherwise, the operation of the device does not differ from that of the known. At the output of the comparison element 10, a mismatch signal appears, under the action of which the actuator 12 moves the feedback potentiometer of the integrating-differentiating unit 4, approximating its transmission coefficient over the derivative to a value equal to the difference of the time constant sensors. When this equality is achieved, the actuator stops,

At the same time, at the output of the measuring and converting unit 6, a voltage of the required polarity is formed and in magnitude proportional to the constant difference ;. time of thermal sensors 1 and 2, the voltage obtained is added in the adder 7 with a voltage setpoint 8 proportional to the time constant of the reference sensor, with the result that the output voltage of the adder 7 is proportional to the desired time constant of the sensor under study. The latter is fixed by the measuring unit 9.

Claims (1)

The invention The device for determining the constant time of thermal sensors according to ed. No. 1642273, characterized in that, in order to improve accuracy, the first and second null-organs, the I element, the inverter and the switch with two switching elements are introduced into it, and the output of the integrating-differentiating unit is connected to the first null-organ the first input of the element I, the output of the subtraction unit through the second null-organ is connected to the second input of the element I and through the normally closed contacts of the first switching element of the switch and the inverter is connected to the second input of the auto-compensator voltage and to the normally open contact there is a switch of the first switching element, a control input connected with the output member and; and the power terminals of the positive and negative polarities of the measuring and converting unit are connected to its first output, respectively, through a normally closed and normally open contacts of the second switching element of the switch.