SU1379746A1 - Device for converting voltage effective values - Google Patents

Abstract

The invention relates to electrical measuring equipment and can be used in the high-frequency conversion of effective values of alternating voltage to equivalent constant voltage. The device contains resistors 1, 8 and 9, thermal converters 2 and 3, amplifier 4, limiting resistor 7, summation block 3, capacitor 11, operational amplifiers 6 and 10. The device has an increased measurement accuracy and an expanded range of input voltages. 1 il.

Description

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The invention relates to electrical measuring equipment and can be used in the high-precision conversion of effective values of alternating voltage to an equivalent constant voltage.

The purpose of the invention is to increase the measurement accuracy and expand the range of input voltages.

The drawing shows the electrical circuit of the device.

The device contains an input circuit consisting of series-connected resistors 1 and the input circuit of the thermocoupler 2. With the output polarity selected, the negative output of the output circuit of the thermocouple generator 3 is connected to a common zero potential bus, the output circuits of the thermocouples 2 and 3 are connected and connected between the bus zero potential and non-inverting input of amplifier 4, the output of which is connected to the first input of summation unit 5, the second input of which is connected to the output of amplifier 6, the house of the device, the first output of the limiting resistor 7 and the first 8 and second 9 resistors in series with the third input of the summation unit 5, and the output of the third amplifier 10, the output of the summing current 5, is connected to the inverting input of the amplifier 10, the capacitor 11 is connected in parallel to the resistor 9, common the connection point of the resistors 8 and 9 and the capacitor 11 is connected to the inverting 11m input of the amplifier 10, the second terminal of the resistor 9 is connected to the first input terminal of the thermal converter 3. Non-inverting inputs of the amplifiers 6 and 10, in ertiruyuschy input of amplifier 4, the second vshody thermocouples are connected to zero potential bus. The values of the resistors 8 and 9 are the same, the values of the resistors connected between the output and the second and third inputs of the summation unit 5 are the same,

The device works as follows.

The converted voltage Uj, heats up the heating of the thermocouple 2 and the appearance at its output of an unbalanced DC signal K a and g, (where K i p is the conversion coefficient of the thermocouple

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2) acting on the input of the amplifier 4, the amplified direct current signal is fed to the first input of the summation unit 5 and is amplified by the second amplifying stage of the compensating feedback circuit; the amplified direct current signal U (i, y, taken from the output of amplifier 6, causes heating of the thermal converter 3, with a DC signal K and p and gji appearing at its output, where K is the conversion factor of the thermal converter 3), reducing unbalanced signal acting on the input of the amplifier 4.

The output voltage U ,,,, simultaneously enters the local positive feedback circuit formed by the first output of the resistor 8, the output of the amplifier 10, the third input of the summation unit 5 and the output of the amplifier 6, When the transmission coefficient over the circuit is equal to one (K , j 1) for the beginning of the working part of the conversion scale of input voltages (K = 1) is established by a slight increase in the value of the resistor 9), which at the end of the transient process reduces the output signal of the direct current at the output of the amplifier 4 to Close to zero. The magnitude of the error signal at the input of the equilibrium 4 is K 4 times smaller (where K is the gain of the amplifier 4). With the same parameters of the forward and reverse conversion circuits, the output voltage of the direct current U is equal to the effective value of the input voltage and 5. The value of the capacitor 11 is chosen so as to ensure a delay in the establishment of a signal in the positive feedback loop, sufficient to ensure the stability of the converter.

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Claims (1)

Apparatus of the Invention A device for converting effective voltage values, comprising a first thermal converter, the input terminals of which serve as the input of the device, the first output terminal is connected to the amplifier input, the second output terminal is connected to the first output terminal of the second thermal converter. the terminal, to the first input terminal of which the limiting resistor is connected, the summation unit, the first the input of which is connected to the output of the amplifier, a capacitor, and the second input terminals of the thermal converters are connected to a common bus, characterized in that, in order to improve measurement accuracy and expand the range of input voltages, two operational amplifiers and two resistors are introduced that non-inverting the inputs of operational amplifiers connected to a common bus; the inverting input of the first operational amplifier is connected to the output of the sum block Worldwide, the output of the first operational amplifier is connected to the output. device and the second input of the summation unit, the second output of the limiting resistor and through the first and second resistors connected in series with the output of the second operational amplifier and the third input of the summation unit, the capacitor is turned on parallel to the second resistor, the inverting input of the second operational amplifier is connected to the common pins of the first and second resistors.