SU947778A1 - Device for comparing cophase alternating voltages - Google Patents

Description

The invention relates to a measuring technique and can be used as a null indicator in metrological installations for checking scale devices.

A device for comparing common-mode alternating voltages is known, containing two parallel channels, each of which has a series-connected repeater, an amplifier and a converter, an input device, the input of which is connected to the outputs of converters, a series-connected MDM amplifier whose input is connected to the output of the subtractor, and GI indicator.

The disadvantage of the known device is the instability of the indicator readings due to the presence of differential instability of the parallel channels.

The closest in technical concern to the present invention is a device for comparing common-mode alternating voltages, containing a sensor sensitivity calibration block, two inputs of which are connected to the device input terminals, a comparison block connected in series, two of which are connected to the sensitivity calibration block outputs, a multiplier , made in the form of a synchronous detector, a low-pass filter and a DC amplifier, the output of which is connected to the output terminal of the device, is formed spruce reference voltage, the input of which is connected to one input of a comparison unit, and

10 output is connected to another input of multiplier 21,

A disadvantage of the known device is the need to manually calibrate it before each measurement,

15 which reduces the speed of the device and leads to an increase in measurement error in the case of comparison of voltages with varying amplitude.

The purpose of the invention is to increase the speed and accuracy of the device.

The goal is achieved by the fact that in a device for comparing common-mode alternating voltages containing a comparison unit, there are only 25 connected bottom-pass filters

Frequency and DC amplifier, the output of which is connected to the device terminal, and multiply. The inputs of the comparator are connected respectively to the input terminals of the device and a differential amplifier is additionally inserted, the inverting input of which is connected to the output of the multiplier, non-inverted input is connected to the output of the comparator and the output is connected to the input of the low-pass filter and to one of the multiplier inputs, and a series-connected converter and adder, the converter's input and another input d cy matopa connected to one of the input terminals of the device, and the output of the adder is connected to the other input of multiplier.

The drawing shows a block diagram of a device

The device contains a series-connected comparison unit 1, two inputs of which are separately connected to the input terminals of the device, a differential amplifier 2 connected to the output of block 1 comparing the NIN non-inverted input, a low-pass filter 3 and an amplifier 4 direct current, the output of which is connected to the output a device terminal, a multiplier 5 and a serially connected converter b and an adder 7. The output of the chopper 5 of the heater 5 is connected to the inverting input of the differential amplifier 2, one input is connected to the output of the diff The potential amplifier 2 and the other is connected to the output of the adder 7, the input of the converter 6 and the other input of the adder 7 are connected to one of the input terminals of the device.

The operation of the device is barely blowing.

Comparable simuson; n (the voltage variables U and U, which are in common, through the input terminals of the device are fed to the inputs of the comparator unit 1, the output of which produces a voltage Oh, proportional to the difference of the compared voltages, i.e. Or (0 - U, j) C, where k ,, is the transmission coefficient of comparison block 1. The voltage Up from the output of comparison block 1 through differential amplifier 2 is fed to one of the inputs of the multiplier 5. Simultaneously, one of the compared voltages and for exemplary, is fed to the input of the converter 6 and one of the inputs of the adder 7. The converter 6 is a linear converter of an alternating voltage into a constant and its output voltage U is by absolute value equal to the compared voltage Uji, taken as an exemplary C), the output voltage of the adder 7 U-, 0, which for any value and is different from .nn Strain U- (from the output of cyNwaTopa 7 enters another input of the pen «1 Resident 5.

The differential amplifier 2, together with the multiplier 5, included in its parallel negative feedback circuit, divides the output voltage Up "(0 ;, - Uij) C of the comparison unit 1 by the output voltage U (O -, / 0 adder 7 As a result, the output of the differential amplifier 2. forms a voltage containing a constant component directly proportional to the amplitude of the output voltage Ojj of the comparison unit 1, equal to the difference of the compared voltages of IC, and UQ, and inversely proportional to the amplitude of the output voltage The and + Uxf of the adder 7, formed from the compared voltage and, received, is exemplary as well as variable. The voltage from the output of the differential amplifier 2 is fed to the input of the low-pass filter 3, which performs its averaging, and from its output through the DC amplifier 4 is applied to the output terminal of the device, wherein the output voltage U4 of the device is equal to

n, ± f (jkiK

where kij, kj |., kg are the transfer coefficients of differential amplifier 2, amplifier 4 of direct current and multiplier 5, respectively.

 At a sufficiently large value of the coefficient kl2.transfer of the differential amplifier 2, the output voltage and the device are

(u.ic.p-U ((. p)

four

,

 WICP- S

® TsSR LSR average values

comparable voltages and. and UnJ "UjCp-UOcp

F-ft is relative ratcp, the nosti compared

voltage U and 0;

kQ. - equivalent transfer ratio

Comparison unit 1, multiplier. 5 and DC amplifier 4.

Claims (1)

Thus, in the proposed device, unlike the prototype, a constant component is formed at the output, proportional to the relative. The difference between the compared variable voltages, which at a constant value of the specified relative difference remains at the same level as the amplitude of the compared voltages changes. This eliminates the calibration operation of the device before measuring, increasing the speed of the device and its accuracy. The use of the proposed device makes it possible to increase labor productivity in the calibration of large-scale devices and to make accurate measurements when the amplitudes of the compared stresses change significantly during the measurement time. Formula of Invention A device for comparing common-mode alternating voltages containing a comparator, a low-pass filter connected in series, and a DC amplifier whose output is connected to the output terminal of the device and a multiplier that improves the speed and accuracy of the device , the inputs of the comparator unit are connected respectively to the input terminals of the device and a differential amplifier is additionally introduced; invertor give its input connected to the multiplier output, not the inverted input is connected to the output of the comparison unit, and the output is connected to the input of the low-pass filter and to one of the multiplier inputs, and the series-connected converter and adder, the converter input and the other input of the adder are connected to one of the input terminals of the device, and the output The adder is connected to another input of the multiplier. Sources of information taken into account during the examination 1. N. Kalinichenko. Differential variable voltage indicators. - Izvesti TPI, 1974, t. 298 .. Tomsk, TSU publishing house, p. 73, rice, 2. 2, Groshev B.L. Differential pointer common-mode voltages, Sat. Standardization and Measuring Technique, vol. 3t Kpiacno RSK, 1977, p. 133-136 (prototype).