SU1223060A1 - Device for measuring index of thermal inertia of resistance thermal converters - Google Patents

Abstract

The invention relates to measuring equipment, to devices for measuring the rate of thermal inertia of thermal converters of resistance, the dependence of resistance on temperature of which can be considered linear in the operating temperature range. The purpose of the invention is to increase the measurement accuracy by stabilizing the power supplied to the resistance thermal converter (TPS) when it is heated. The device contains a TPS heating source 1, current pulses of a given magnitude and duration forming at its output, a current to voltage converter 2, a TPS 3 test subject, quad 4, a differential 5, a pulse detector 6, a resistive voltage divider 7, an adder 8, a functional converter 9, a current regulator 10, a comparison circuit 11 and 12, a time interval meter 13 consisting of a counting pulse generator 14 and a counter 15. All the blocks in the block diagram are interconnected in a certain way, which allows objects of the invention. 1 il. (L with 1C y with about O)

Description

The invention relates to a measurement technique, in particular, to devices for measuring the thermal inertia indicator of resistance thermal converters, the dependence of resistance on temperature of which can be considered linear in the operating temperature range.

The aim of the invention is to improve the measurement accuracy by stabilizing the power applied to the thermal converter when it is heated.

The drawing shows a block diagram of the proposed device.

The device contains a source 1 for a thermal converter, for example, a current source that generates current pulses of a given magnitude and duration at its output, a current-voltage converter 2, for example, a calibrated shunt, a thermal converter 3 under test, square A, a differentiator 5, a pulse detector 6, a resistive a voltage divider 7, an adder 8, a functional converter 9, a current regulator 10, two circuits 11 and 12 of comparison, a meter of 13 time intervals consisting of a generator of 14 counting pulses and a counter 15 pulses.

The device works as follows.

The heat source 1 generates. rectangular amplitude and duration adjustable current pulses. In order to ensure the exponential nature of the increase in temperature and, consequently, the resistance of the thermocouple with the linear dependence of the resistance on temperature, it is necessary to heat the thermoconverter at a constant input power.

For this, the current I (t) flowing through the thermocouple should change according to the law,

Kt)

(one)

WHAT can be obtained if the current Ip (t), flow through the current regulator 0 10, connected in parallel to the thermal converter, varies along

to the law

Ip (t)

I - i.

(2)

where 1d is the initial current, the value of which is chosen depending on

to

20

-15 25

thirty

35

40

2230601

the type of thermal converter used;

E | C - the initial resistance of the thermocouple;

R (t) is the current value of the resistance of the thermocouple, depending on its temperature t.

Current regulator 10 can be made on the basis of a transistor connected by a variable resistance circuit. To obtain the indicated current dependence, the control input must be supplied with a voltage varying according to the same law that is formed by using the adder 8 and the functional converter 9. The latter can be made as an operational amplifier, to the o6paiT circuit of which A resistor with a resistance of / 1k is turned on, and an electrically controlled nonlinear variable resistor is connected to the input, for example, based on a transistor.

When current flows through current converter 2, a voltage proportional to current 1 is generated at its output, which is fed to the second input of the adder 8 and the input of the functional converter 9, to another input of which the voltage of the resistance thermocouplers is received, which is proportional to its resistance. In this case, the output of the functional converter appears voltage, proportional

the vital value - 1 p

which arrives at the first input of the adder, and at the output of the adder - a voltage proportional to the value (I. -1

) which arrives on

the control input of the current regulator, as a result of which the current flowing through it is changed according to the law described by expression (2).

The voltage removed from the thermocouple is 3.

U (t) l (t) .R (t)) KjR (t), K (3)

K. UR.

is applied to quad 4, from the output of which a signal proportional to the value of) to R (t) and varying exponentially, is fed to the pulse detector 6. The pulse detector records the maximum value of the derived signal

and iidT

and gives it to

a resistive divider with division factors K and K 1, where 1 is the base of the natural logarithms; K is a number close to one. From the outputs of the resistive divider 7, the voltage and K / K are fed to the first inputs of the comparison circuits 11 and 12, the second inputs of which receive the signal U (t) from the output of the differentiator. The comparison circuit 12, to which the reference voltage is applied, produces a starting pulse for the time interval meter 13, and the voltage level circuit 11, for which the stop pulse is applied. Since the reference levels differ from each other by a factor of 1, and the voltage at the output of the differentiator varies exponentially, the time interval between the moments of operation of the threshold circuits is equal to the value of the thermal inertia indicator of the thermoconverter under test.

Claims (1)

Invention Formula A device for measuring the thermal inertia index of resistance thermal converters, comprising Editor O. Yurkovetska Compiled by V.Kulikov Tehred I.Gaydosh Proofreader S.Shekmar Order 1702/43 Circulation 778 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Branch PSh1 Patent, Uzhgorod, Proektna St., 4 heat source of thermal converter, a differentiator, the output of which is connected to the input of a pulse detector and the first inputs of two circuits 5 comparisons, the second inputs of which are connected to the output of the resistive divider connected to the output of the pulse detector, and the outputs are connected to the time interval meter. 0 characterized in that, in order to improve the measurement accuracy by stabilizing the power, hanging on the thermal converter, it introduced a quad, current regulator, 5 current-to-voltage converter, functional converter and adder, the first input of which is connected to the first input of the functional converter and the converter's current-to-voltage converter connected between the output of the heating source Tfep-converter and the thermal converter under test, the outputs of which are connected to the second input of the function converter 5, the converter and through the quad are connected to the input of the differentiator, while the current regulator is connected parallel to the thermal converter, the control input of which connect dinene with the output of the adder.