SU1216678A1 - Apparatus for measuring thermal lag index of resistance thermal converter - Google Patents

Abstract

The invention relates to a measurement technique and permits an improvement in the measurement accuracy of the thermal inertia indicator. By taking into account the non-linearity of the thermal converter. The device contains a thermal converter heating source 1, a current-to-voltage converter 2, a tested thermal converter 3, a key 4, a measuring current source 5, a functional converter 6, adders 7 and 14, an operational amplifier 8 with resistors 9-11, an ambient temperature setpoint 12 medium, inverter 13, storage unit 15, comparison circuit 16, time interval meter 17, inclusions of counting pulse generator 18 and pulse counter 19, and key 20. Introducing new elements and forming new connections between ementami device allows to measure the time interval of the heating and cooling thermal converter 3 which is equal to the index of thermal inertia. 1 il. from $ 3 (L TP K) GR 00

Description

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The invention relates to the field of measuring technology and can be used when checking the characteristics of thermal converters,

The purpose of the invention is to improve the measurement accuracy of the thermal inertia index by taking into account the thermodynamic conductivity of the resistance.

In the drawing, the npi-w is one block diagram of the device.

The device contains a heating source of thermal converter 1, for example, a generator that generates current pulses of a certain amplitude and duration, Current converter 2 to voltage, for example, a resistor shunt, forming a signal (voltage) proportional to current to its terminals, test C; thermal converter 3, key 4. measuring current source 5, functional converter 6, for example, a diode With a nonlinear transfer function, back with respect to the function of a thermal converter that establishes a connection between its resistance and temperature, the first adder 7, on operational amplifier 8 with recorders 9-11, and the resistance of the resistors Rg, R and selections such that Rg / R., where e is the base of natural logarithms, the setpoint 12 of the ambient temperature, which can be used as n, any thermal converter, a output signal proportional to the ambient temperature, an inverter 13, a second adder 14, a storage unit 15, for example a pulse detector with a reset circuit, a comparison circuit 16, a meter 17 time slots, including a counting pulse generator 18 and a pulse counter 19, a switch 20, switched on between the output of a measuring current source and a thermoconverter terminals.The presence of a switch 20 in the device depends on the circuit of the measuring current source 5 used. In principle, the key 20 may be missing.

The device works as follows.

When starting the device (start-up circuit not shown) current source 1

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produces a square, adjustable in amplitude and duration, current pulse that arrives through. Cutting the voltage-to-current converter 2 to the thermal converter 3 and heating it to a certain temperature T. At the end of the pulse, the heating of the thermal converter ends and its temperature begins to decrease exponentially, to an ambient temperature, then. At the same time, the law of change in the resistance of the thermal converter in time will differ from the exponential due to the nonlinear characteristic of the thermal converter.

During the action of the heating pulse, the keys 4 and 20 are closed by signals from the output of the converter 2 current to voltage, after the end of the pulse, the keys 4 and 20 are opened, while the current from the measuring current source 5 begins to flow through the thermocouple 3, and accordingly, a voltage appears at the input of the functional converter 6, which is proportional to its resistance, and depends nonlinearly on its temperature. In this case, at the output of the functional converter, the characteristic of which is chosen such as to ensure the linearization of the signal from the thermal converter, there appears a voltage directly proportional to the temperature of the thermal converter. This signal, together with a crush proportional to the ambient temperature Td from the sensor 12, the pass csm through the inverter 13, goes to the inputs of the first cy iMaTopa 7, at the output of which a signal proportional to the value () appears. The signal from the output of the adder 7 simultaneously with the signal from the output of the inverter 13 is fed to the inputs of the second adder 14, the output of which forms a signal proportional to the value (To +). This signal, through the storage unit 15, where it is memorized, before the beginning of the influence of the next heating pulse, goes to the first BbDi input of the comparison circuit 16, to the second input of which a signal is output from the function converter, proportional to the temperature of the thermal converter,

Thus, at the moment of termination of the heating current pulse, signals (To + LTO) and (That + DT / e) are sent to the comparison circuit and the signal is generated to the time signal meter, which from this moment will begin the delay of the cooling time of the thermal converter, At the moment The time when the temperature of the thermal converter becomes equal to T Ta + DT / e, the comparison circuit produces a stop pulse, and the time count stops.

Since overheating of the thermocouple will decrease by a factor of за times within the measured time interval, this interval is equal to the value of the thermal inerg index of the thermocouple resistance.

Claims (1)

Invention Formula A device for measuring the thermal inertia index of a resistance thermocouple containing a heat source of a thermoconverter measuring current source, a key, a storage unit and a comparison circuit whose output is connected by V.Ivanov Editor Order 996/53 Compiled by B. Kulikov Tehred S. Migunova Corrector Circulation 778 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Branch PPP Patent, g. Uzhgof) od, st. Project, 4 A time interval meter consisting of a counting pulse generator and a pulse counter, characterized in that In order to improve the measurement accuracy by taking into account the inconsistency of the thermal converter, the resistance, a current-to-voltage converter, an ambient temperature setpoint meter, an inverter, two adders and a functional transducer have been introduced into it. the distributor, whose input is connected via a switch to the terminals of the test thermoconverter connected to the measuring current source, and the output is connected to the first input of the first adder, the second input of which through an inverter is connected to the output of the temperature setter environment, and the output is connected to the first input of the second adder, the second input of which is connected to the output of the inverter, and the output is connected to the first input of the comparison circuit through the memory unit, the second input of which is connected to the output of the function converter, while the heat source is connected to the thermal transfer terminal. through the current-to-current converter, the output of which is connected to the control input of the key. Corrector V.But ha