SU976394A1 - Digital voltmeter - Google Patents

Description

The invention relates to electrical measuring equipment and is intended to measure the rms value of periodic voltages of complex shape.

A device is known comprising a logarithmic amplifier, a processing unit, a linear detector, a first integrator, an indicator, a variable voltage selection unit, a quad, a second integrator, and a correction factor selection unit 1.

A disadvantage of this device is the limited range of operating frequencies and the ability to measure periodic signals of complex shape only in the area of sound frequencies.

A device is known comprising a voltage-to-frequency converter with a square-law conversion function, an input signal period selector, a control unit, an input switch, a key, a counter, a code matching circuit, a bit compensator voltage compensator, and a display unit 2.

 The disadvantage of the device is the limitation of the frequency range of the measured signals to the sound field.

It is also known a device containing a code-analog converter, whose information input is connected to the input of a voltmeter and,. the period determining unit (forming unit), and the output to the information input of the calculating unit, the output of which is the output of the voltmeter, and the other output is connected

10 with the first input by the control unit, the second input of which is connected to the first output of the period determining unit. In addition to the listed nodes, the voltmeter additionally contains a frequency multiplier, an OR element, and a pulse generator. The voltmeter is designed to measure the periodic voltages of the infra-low NW frequency range.

20

The disadvantage of this voltmeter is the impossibility of measuring, with a predetermined error, the voltages of the range of sound frequencies.

The aim of the invention is to | expand;

25 widening of the frequency range by increasing its upper limit.

The goal is achieved by the fact that a digital voltmeter containing an analog-code converter, an information input of which is connected to

the input bus and the input of the period determination unit, and the output - to the information input of the computing unit, the first output of which is connected to the output bus, the second output - to the first input of the control unit, the second input of which is connected to the first output of the detection unit; , trigger, pulse shaper, control counter, switch, frequency shaping unit, the output of which is connected to the first input of the switch, the output of which is connected to the first input of the AND element and the third input of the control unit, and The input is connected to the output of the control counter whose input is connected to the output of the pulse former and to the first trigger input, the second input of which is connected to the output of the ordinate number counter, and the output to the input of the pulse former, and the second input of the I element is connected to the second the output of the period determination unit, and the output is -c with the control inputs of the analog-code converter and the calculation unit, with the input of the count of the number of ordinates connected by S. the output of the control unit.

The drawing shows the block diagram of the proposed digital voltmeter ™ pa.

The voltmeter contains an analog-code converter 1, a calculation unit 2, a period determination block 3, an AND 4 unit, a frequency shaping unit 5, a switch 6, a control meter 7, a control block 8, a count number 9 of the ordinate, a trigger 10, a pulse former 11.

The inputs of the analog converter 1 and the period determination unit 3 are connected to the input of a voltmeter. The output of the transform. Tel 1 analogue - code through the block 2 of calculation is connected to the output of the voltmeter. The first output of the period determining unit 3 is connected to the control unit 8, and the second output of the unit 3 is connected to the second input of the element AND 4. The frequency shaping unit 5 is connected to the first input of the element 4 and the third input of the control unit 8 via the first input of the switch 6. The output of the element 4 is connected to the control inputs of the converter 1 analogue code and the block 2 of calculation. The second input of the switch 6 through the counter 7 control is connected to the driver of the pulse generator 11 and to the first input of the trigger U, the output of which is connected to the input of the driver 11, The second input of the trigger 10 through the counter 9 of the number of ordinates is connected to the output of the control unit 8, the first input of which connects with the second output of the calculation block 2

U.Stroyistpo works as follows.

The input signal is fed to the input of the converter 1 analogue – code and to the unit 3 for determining the period of the input signal. In the period determination unit 3, the first and second periods are extracted, the output signal and the enabling signals are formed at its first and second outputs, respectively.

After starting the voltmeter, the second input of the control unit 8 receives the enable signal from the period determination unit 3, which activates the control unit 8 during the first period of the measured signal. At the same time, the highest frequency is fed to the counter 9 of the number of orders from the frequency shaping unit 5 through the switch 6 and the control unit 8. When using a binary grid of frequencies () in the case of overflow of the counter 9, the number of ordinates and trigger 10, the driver 11 is triggered, which sets trigger one 10 and increases the contents of counter 7 by one. The latter switches the switch 6, so that ordinate the frequency is reduced by half. At the same time, the second cycle of forming the starting frequency of the converter 1 analogue-code begins. Then the cycle repeats until the end of the first period of the input signal, i. Thus, during the first period of the input signal, the starting frequency of the converter 1 is formed. analog - code.

After the end of the first period of the input signal, the period determining unit 3 from the first output generates a blocking potential, by which the determination of the clock frequency and the number of ordinates on the period of the measured signal stops, and from the second output of unit 3 the resolution signal is applied to the second input of the And 4 element for the duration of the input signal period selected in the previous period of the measured voltage, the clock frequency through the switch b is output to the inputs of the analog-code converter 1 and the computing unit 2.

Converter 1 analogue — the code starts at each cycle and the ordinate codes arrive at block 2 of the calculation. The number of starts of the converters is counted by calculation block 2. The measured voltage ordinates Xj (t) and the number of ordinates S are used to calculate the mean square value of the measured voltage.

At the end of the second period, block 2 generates a pulse at the first input of control block 8, through which the measurement cycle is pumped. The digital voltmeter is ready to receive the next trigger signal,

. The discrete determination of the Period in the proposed voltmeter is always determined by the size of the sampling step, which is equivalent to the fact that the error of the frequency multiplier is equal to

°

about other things. equal conditions, provides an increase in the upper limit of the frequency range.

Thus, the additionally introduced blocks and the connections between them make it possible to increase the upper limit of the frequency range of the voltmeter, which contributes to the expansion of its scope.

Claims (3)

1. USSR author's certificate number 402813, cl. G 01 R 19/02, 1971. 2. Authors certificate of the USSR 0 367389, cl. G 01 R 19/25, 1971. 3.Smelov V.V. Digital measuring equipment infra-low frequencies. M., Energie, 1975, p.70 (prototype).