SU601620A1 - Ac digital voltmeter - Google Patents

Description

matara through relay null-0: rgan is connected to the control input of the scale converter and the time selector whose input is connected to the output of the voltage – frequency converter, and the output to the digital reading unit.

In the drawing, a block diagram of a VoltMiTipa is represented.

The digital AC volt mbtr contains an input sumgaty /, to the second input of which is connected a source of 1 modulator but white noise. A 2, and the output of the adder through the broadband amplifier 5 and the converter is valid, their values 4 are connected to the input of the voltage converter in step 5 and the input of the selective unit 6. The output of the latter is connected to the output adder 7 via a controlled Scale Converter 8. To the second input of the output adder 7 A signal from the modulating white noise terminal 2 is output.

The output OUT1NO1PO of the sum-ator 7 through the relay null-ory I consisting of amplifier 10 and Schmidt trigger //, is connected to the control inputs of the modem selector 12 and the scale converter 5. In, the selector 12 is connected to the output of the voltage converter at frequency 5 and the output is to the digital readout block 13.

It is known that white noise modulated by a meander does not change its statistical properties. If you apply modulated white noise to one of the inputs of adder 1, the level of ne exceeds the intrinsic noise of broadband amplifier 3, and the other input the measured signal, then it is obvious that white noise will not affect the operation of the measuring path (amplifier 3 , the transducer of actual values of the transducer n: alr eni and -frequency 5, time selector 12 and digital reading unit 13). At the same time, at the output of the Transformer: the voter of the acting values, 4 with the help of the electoral block 6 and it is possible to select harmonic signals with frequencies that are multiples of the modulated Meander frequency. Thus o6pia3OM, iHa, the output of converter 4 yields a constant voltage proportional to the effective value of the measured alternating current, and the output of the selective unit 6 is a test signal carrying information about the multiplex error of the measurement path.

.Production of the most recent conversion of the measured value to the frequency, we obtain at the output of the time selector 12 the number of pulses, indicated by the reading unit 13. The selective unit 6 connected to the output of the effective value converter 4 extracts the test signal of the source of modulated white noise | scale transformer | p1azovatel 8 leads him to the scale of the input test value.

When the input voltages of the output CyMMaTOpiB 7 are not equal, a difference signal appears at its output, which is fed to

the input of the relay null organ 9, consisting of amplifier 10 and Schmidt trigger 11. The trigger is set to a position corresponding to the inequality sign and connected to its output controlled time selector 12 either increases or decreases the duration of writing of the resulting Pulses to the digital reading unit 13 At the same time, the control input of the controlled scale converter 8 is set to a voltage of zero-iopraHa 9, at which the change of the sign of its input match, and the trigger // is turned into the opposite state the Thus, the voltage at the control input of the time selector / 2 changes with some natural frequency, the amplitude of oscillations is such that the change in the output voltage of the controlled scale converter 5 is equally resolvable. the null organ. 9. As a result of this, continuous correction of the measurement path occurs.

The use of a modulated white noise as a test signal favorably distinguishes this digital AC voltmeter from the known ones, since the stability problem of the wideband amplifier is eliminated, the response speed is improved due to the fact that the measurement path is continuously corrected, the accuracy is improved, as it is not corrected Only additive, but multiplicative component of error.

Claims (2)

Invention Formula An AC digital voltmeter containing an output adder, a digital readout unit and in series a connected input adder, the first input of which is connected to the input signal bus, a wideband amplifier, an actual value converter, the converter is tuned to a frequency that differs in speed, A 1-modulated white noise source, a selective block, a large-scale converter, a time selector and a null-relay source are entered into it, and the source output is modulated of white noise is connected to the second input of the input adder and the first input to the output adder, the second input of which via inverter M1asshtabny and the selective block is connected to the output of the transducer of actual values, the output of the output adder through the relay null organ to the control inputs of the large-scale converter and the time selector whose input is connected to the output of the voltage-frequency converter, and the output to the digital reading unit. Sources of information taken into account during the examination: 5 1 Patent of England No. 1127442, cl. 1969. G4H, 2. USSR Author's Certificate No. 386344, 601620 6 G 01 R 13/02, 1971.