SU1215038A1 - Apparatus for measuring amplitude of alternating current voltage - Google Patents

Abstract

The invention relates to a measurement technique and makes it possible to increase the accuracy of measuring the amplitude W of an alternating current voltage by taking into account its shape. The device contains a switch 1, an alternating voltage to constant voltage converter 2, a voltage-to-frequency converter 3, a key 4, a reversible counter 5, a memory unit 6, a digital controlled voltage divider 7, a control unit 8 and an indication unit 9, digital signal converter 10, divider 11, multiplier 12, amplitude limiter 13 and input bus 14. In the description, expressions are given that determine the relationship between the result of the change and the true value of the signal amplitude and the output signal of the multiplier 12. In addition, april ages that explain the principle of operation of the device Il. i (L

Description

The invention relates to electrical measuring technology.

The purpose of the invention is to improve the accuracy of measuring the amplitude of the AC voltage by taking into account its shape.

Fig. 1 shows a functional diagram of an apparatus for measuring AC voltage; Fig. 2 illustrates stress plots explaining the principle of its operation.

The device contains serially connected switch 1, variable voltage to constant voltage converter 2, voltage to frequency converter 3, switch 4, reversible counter 5, memory unit 6, digital controlled voltage divider 7, control unit 8, the outputs of which are - not with the control inputs of the switch 1, the variable voltage converter 2 to the constant, the key 4, the reversing counter 5 and the memory block, the outputs of which are connected to the display unit 9 and serially connected digital-to-analog converter U, divider 51, multiplier 12 and amplitude limiter 13, the output of which is connected to the input of the digital controlled divider 7 voltage, the output of which is connected to the first input of the switch 1, the second input of which is connected to the second input of the multiplier 12.

The proposed device for measuring the amplitude of the alternating current voltage provides the formation of a reference voltage supplied to the input of the digital controlled voltage generator 7 and in shape and frequency coinciding with the measured voltage on the bus 14, which improves the accuracy of the measurement.

The device works as follows.

Initially, the switch I, via a signal (Fig. 2a) from the control unit 8, connects the measured voltage (Fig. 2b) to the input of the AC voltage converter 2 into a constant, where the AC input voltage is converted into a constant (Fig. 2c), at the same time, to the control input of the converter 2 alternating voltage

a constant zeroing pulse (Fig. 2e) is not received from control unit 8. The resulting DC voltage is converted to the frequency

using a voltage-to-frequency converter 3. Next, the control unit 8 generates a pulse (Fig. 2d) of constant duration acting on the control input of the key 4, as a result of which the pulses from the voltage-to-frequency converter 3 are recorded in the reversible counter 5 operating in the forward counting mode. In the reversible counter 5, the number is

Hell is proportional to the amplitude of the signal on the input bus 14. Link between the measurement result and the true value of the amplitude of the signal

determined by hyphenation

And A, k, (1).

five

0

five

0

where Hell is the result of gross measurement. neither the amplitude of the input sig-

Nala;

, A is the true value of the input signal amplitude; Kg is the transfer coefficient of the variable-to-constant voltage converter 2 ().

By the decay of a pulse of constant duration (Fig. 2d), control unit 8 generates a pulse recording the readings of the reversible counter 5 (Fig. 2e) into memory block 6. For the duration of the write pulse, a code appears at the outputs of the memory block 6 corresponding to the minimum transmission coefficient of the digital controlled voltage divider 7, which prevents the digital controlled voltage divider 7 from being outdated for the zero-pulse action period (Fig. 2e) . Simultaneously with the recording pulse, the control unit 8 switches the switch 1 (Fig. 2a). Through the interval ti, equal to the switching time of the switch 1, from the decay of a constant pulse (Fig. 2d), the control unit 8 f speeds up the zeroing pulse (Figure 2e), according to which the voltage at the output of the converter 2 of the variable

5 the voltage in the constant becomes., Equal to zero. From the decay of the write pulse (Fig. 2e), at the outputs of block 6 {of the memory, a code appears corresponding to ..

3

Ad number, which through digital-to-analog converter 10, matching the analog divider with the digital memory block, goes to divider 11, the output voltage of which is inversely proportional to Ad. Simultaneously with this, control unit 8 generates switching | pulse (FIG. .2) reversible counter 5 to the countdown. The result of calculating the inverse Hell is sent to the first input of the multiplier 12, the second input of which receives the measured signal from the input bus 14. & 1) the multiplex i 2 code signal is described by the expression

Ls Vit)

A R:

at

(2)

where p (t) is a function describing

change in signal over time;

B is a constant value. Thus, the signal at the output of the multiplier 12 has the form of the measured voltage on the bus 14, does not depend on the amplitude of the measured voltage, but is a function of the coefficient of the forming transducer 2 of an alternating voltage into a constant from the form of the measured voltage. To eliminate this dependence, an amplitude limiter 13 is used. A signal from the output of the amplitude limiter 13, limited in level, is fed to the power bus of the digital controlled voltage suppressor 7. The coefficient in the expression (2) is chosen from the condition that Cd I output signal of the multiplier 22 has the maximum possible value at which the ampere limiter 13 still does not introduce amplitude restrictions. The transfer ratio of the digital controlled voltage divider 7 is determined by the code at the outputs of memory block 6 and is proportional to the number A. The voltage output from the digital controlled voltage divider 7 is connected via a junction switch J of the converter J to the constant voltage converter 2. 3 transducer input to frequency input

Next, the control unit 8 generates, impulse9 constant duration15038

Fig. 2d, acting on the control input of the switch 4. As a result, the pulses from the output of the voltage-frequency converter 3 begin to flow to the reversible counter 5 operating in the countdown mode. In the reversible counter 5, the first difference is obtained between the result of the rough measurement of the input

10 voltages; on bus 14 and on the output voltage of the digital controlled voltage divider 7. In the process of obtaining the first difference, the block 8 of the obstruction is again connecting the measured

15, the voltage through the switch 1 to the input of the inverter 2 of the alternating voltage into a constant voltage and switches the operating mode of the reversing meter 5 to a direct account. Then

20, the control unit 8 generates a pulse of constant duration (FIG. 2d), which acts on the control input of the switch 4, and the pulses from the output of the voltage-frequency converter 3 begin to flow to the input of the reversing counter 5 and are added to the code the first difference. As a result, we obtain the first corrected result of A, measuring the amplitudes of the input signal, and, consequently, K, K. By the decay of a pulse of constant duration (Fig. 2d), the control unit 8 again forms a 4 record pulse (Fig. 2e) of the readout of the reverse

35 counter 5 in memory block 6. During the time of the action of the write pulse, the code corresponding to the minimum transfer coefficient of the digital controlled voltage divider 7 appears at the outputs of the memory block 6. Simultaneously with the write pulse, the control unit 8 switches the switch 5 (FIG. 2a). After a period of time t from the decay of a pulse of constant duration, the control unit 8 forms a zeroing pulse (Fig. 2e), according to which the voltage at the output of the transducer 2 of the variables-iHoro voltage is set to zero. On the decline of the write pulse (fig. 2d), the control unit 8 makes a change in the direction of the counter of the reversible counter 5 (fig.2g). At the same time, a code corresponding to the number A, which via digital-analogue, appears at the outputs of the memory block b transformed; The transmitter 10 is fed to the input of the divider 11, where the calculation of the inverse of A) takes place. The result of the calculation goes to the first input of the multiplier 12,; the second input j of which receives the measured signal from the input bus 14. Since K 7. ,, y n, uj ,,, j ,, and since the level of limiting the amplitude limiter 13 10 is constant, the signal at the output of the amplitude limit 13 after the first correction is closer in shape to the voltage on the input bus 14 than before the correction. The resulting 15 signal is fed to the power bus of the digital controlled voltage divider 7, the transmission coefficient of which is determined by the code at the outputs of memory block 6, the proportional number of A. The voltage output from the digital controlled voltage divider 7 is through a switch 1 and the variable voltage converter 2 to the constant is fed to the 25th input of the voltage converter 3 to the frequency.

Next, the control unit 8 generates a pulse of constant duration ((| ig.2g), as a result of which through the DZ cut key 4, pulses from the output of the converter 3, voltage to frequency, to the input of the reversing counter 5, operating in the reverse counting mode, pass As a result, 35 the second difference between the first corrected result and the output voltage of the digital controlled divider voltage 7 is obtained. Next, the control unit 8 generates a pulse (Fig. 2a), connects the measured voltage {input tire 14) cher Without switch 1 to the input of the variable voltage converter 2 to constant and switches the operation mode of the reversible counter 5 to a direct account (Fig. 2g). After that, the control unit 8 generates a pulse of constant duration (Fig. 2d), 50 which acts on the control input of the switch 4, and the pulses from the output of the voltage converter 3 to the frequency arrive at the input of the reversible counter 5, where 55 are summed with the second difference code resulting in a second corrected A-measurement result

voltage amplitude on the input bus 14. Similarly, continuing the measurement process, by correcting the conversion coefficient of the variable voltage converter 2 and the voltage converter 3 frequency converter, you can get an N-corrected result that is free from the error introduced by the converter 2 alternating voltage to constant voltage and voltage transformer 3 to frequency, due to the fact that the voltage form at the output of the digital controlled voltage divider 7 approaches the voltage form audio input on bus 14.

Accounting for the shape of the measured AC voltage by introducing an analog multiplier reduces the error due to the influence of the shape of the measured voltage on the AC-DC converter.

The correction of the measurement result in both the known and proposed MCW device ends when the equality

and.

er about

(3)

where uf. 1, is the average voltage on the cumulative capacitance of an amplitude detector for a measured voltage j

.oa is the average voltage across the cumulative capacitance of the amplitude detector for the reference voltage. . neither

And, p. "," -A. K, (K, is the transmission coefficient of the amplitude detector for the measured voltage, Ac is the true value of the amplitude of the measured voltage. AC {corrected The transfer coefficient of the amplitude detector for the measured signal, - the transmission coefficient of the amplitude detector for reference voltage).

Claims (1)

Invention Formula An apparatus for measuring the amplitude of an AC voltage comprising a switch connected in series, the first input of which connected to the output bus, an AC / DC converter, a voltage-to-frequency converter, a key, a reversible counter, a memory unit and a digital controlled voltage divider, the output of which is connected to the second input of the switch, as well as the control unit, the corresponding outputs which are connected to the control inputs of the switch, the key, the reversible counter and the memory block, and the display unit, the inputs of which are connected to the outputs of the memory block. characterized in that, in order to improve accuracy, the outputs of the memory block are additionally connected in series digital-to-analog converter, divider, multiplier, the second input of which is connected to the input-. bus, and the amplitude limiter connected to the input of the digital controlled voltage divider, while the auxiliary output of the control unit is connected to the control input of the alternating voltage converter to a constant. but 8. 2