SU1541517A1 - Electricity meter - Google Patents

Abstract

The invention relates to electrical measuring equipment and is intended to measure direct and alternating current electricity. The purpose of the invention is to improve the measurement accuracy by reducing the error due to the coincidence of the feedback pulses with the switching points of the switches. After multiplying the signals from the current and voltage sensors, the product is converted into the pulse frequency and the position of the number of pulses. Fixing the duration of the feedback pulse at the moments of switching the switches avoids the accumulation of errors from period to period, which accordingly leads to an increase in the measurement accuracy. This operation is performed by introducing the first counter 11, the third switch 12, the threshold element 13, the first and second elements 2I 14 and 16, the first and second elements 3I 15 and 17, the second and third counters 18 and 19, and the first and second triggers 20 and 21. In addition, the electricity meter contains first and second switches 1 and 8, multiplier 2, inverting DC amplifier 3, reference current source 4, first and second capacitors 5 and 6, resistor 7, pulse generator 9, and reversing counter 10 .1 il.

Description

The invention relates to electrical measuring equipment and is intended to measure direct and alternating current electricity.

The purpose of the invention is to improve the measurement accuracy by reducing the error due to the coincidence of the feedback pulses with the switching points of the switches.

The drawing shows the structural and functional diagram of the electricity meter.

The electricity meter contains the first switch 1, the multiplier 2t inverting amplifier 3 DC, 4 reference current source 4, the first 5 and second 6 capacitors, a resistor 7, a second switch 8, a generator 9 pulses, a reversible counter 10, the first counter 11, the third switch 12 , threshold element 13, first element 2И 14, first element ZI 15, second element 2I 16, second element ZI 17, second 18 and third 19 counters, first 20 and second 21 triggers, moreover, the counter input for connecting the current input signal through the first switch 1 is connected to the first input of multiplier 2, the second input of which is the counter input to which a voltage signal is applied, the output of the multiplier 2 is connected to the input of a DC inverting amplifier 3, the output of the reference current source 4, the first plates of the first 5 and second 6 capacitors and the first terminal of the resistor 7, the inputs of the threshold element 13 and the second switch 8 are connected to the output of the inverting amplifier 3 of direct current 3, the output of the threshold element 13 is connected to the first inputs of the first 14 and second 16 elements 2I, and The output is to the counting input of the reversible counter 10, the outputs of the first 14 and second 16 elements 2I are connected to the inputs of the installation of 1 of the first 20 and second 21 triggers, respectively, and the outputs of the latter are connected to the first and second inputs of the third switch 1.2, whose output is connected to the second terminal of the resistor 7, the output of the pulse generator 9 is connected to the input of the first counter 11, the second inputs of the first 15 and second 17 ZI elements, the direct output of the first counter 11 is connected to the control inputs of the first 1, second 8 and third 12

five

0

five

0

five

0

five

0

five

switches, the control input of the reverse reversible counter 10, the second input of the first element 2I 14 and the first input of the first element ZI 15, and the inverse to the second input of the second element 2I 16 and the first input of the second element ZI 17, the outputs of the first 15 and second 17 elements ZI are connected with the inputs of the installation of the first 20 and second 21 flip-flops, the outputs of which are connected respectively to the third inputs of the first 15 and second 17 ZI elements, the outputs of the second switch 8 are connected respectively to the second plates of the first 5 and second 6 condensate moat.

The electricity meter works as follows.

In the initial state, the first 1I, the second 18 and the third 19 counters, the first 20 and second 21 triggers are in the zero state. The pulse generator 9 generates a sequence of pulses of a stable frequency, which is fed to the input of the first counter 11 and the second inputs of the first 15 and second 17 ZI elements, but the latter are blocked by zero signals at the third inputs. The output frequency of the pulse generator 9 is selected from the conditions of the accuracy of the generation of feedback pulses, and the conversion factor of the first counter 11 is such that its output frequency is twice the maximum frequency of the input signal. The recalculation coefficients of the second 18 and third 19 counters are chosen equal and the duration of the feedback pulses is determined. In the first half-period of oscillation of the output signal of the first counter 11, a single signal is present on its direct output, and zero on the inverse. The transfer coefficient of the first switch is 41, the first capacitor 5 is connected to the output of the inverting amplifier 3 DC, the output of the first trigger 20 is connected via a third switch 12 to a resistor 7, and the reversing counter 10 sums the pulses to the counting input. At the output of the inverting DC amplifier 3, a voltage is formed proportional to the integral of the sum of the currents coming from the current source 4 and the multiplier 2,

In the second half-period of oscillation of the output signal of the first counter 11, a zero signal is present at its direct output, and in the inverse one is single, therefore the transmission coefficient of the first switch 1 is -1 and the output signal of the multiplier 2 is reversed to the output of the inverting amplifier 3 The current is connected to the second capacitor 6, the output of the second trigger 21 is connected via a third switch 12 to a resistor 7, and the reversible counter 10 subtracts the pulses fed to the counting input. At the output of the inverting DC amplifier 3, a voltage proportional to the integral of the voltage 6 is formed, decreasing by a value determined by the volt-second feedback pulse area.

If the signal at the direct output of the first counter 1I switches from a single state to zero at a single signal at the output of the first trigger 20, which corresponds to the coincidence of the end of the first half period with the feedback pulse, then the zero signal from the direct output of the first counter 11 blocks the first element of ZI

5 15, and the second counter 18 records the feedback pulse duration dO, which coincides with the first half period. In this case, the third switch 12 disables the first trigger 20 from

current from the source 2Q resistor 7, and at the first condensate35

4 currents and multiplier 2.

When the output voltage of the inverting amplifier 3 reaches a constant switching level of the threshold element 13, a short pulse is generated at its output, which is fed to the counting input of the reversible counter 10 and the first inputs of the first 14 and second 16 elements 2I. In the first half-period, a second signal is present at the second input of the first element 2I I4, so a pulse arises at its output that sets the first trigger 20 to the one state, while the second element 2I 16 is blocked by a zero signal at its second input coming from the inverse output of the first counter 11. Switching the first trigger 20 to a single state permits the passage of the output frequency of the generator 9 pulses to the input of the second counter 18. After the latter is full, a pulse is generated at its output th first flip-flop 20 returns to the zero state. Thus, at the output of the first trigger 20, a feedback pulse of stable duration and amplitude is generated.

In the second half-cycle, a feedback pulse is formed similarly with the help of the second elements 2И 16 and ЗИ 17, the third counter 19 and the second trigger 21. During the time of the feedback pulse, the output voltage of the inverting amplifier 3 DC generated in the first half-period the first capacitor 5, and in the second. - the second capacitor 5 remembers the residual voltage

Y / 2

U,

C1

 p iCtbijdt C o

Wooi. U0 (C-JJCJ) RC RC

- to;

After the end of the second half-period, the second switch 8 again switches the first capacitor 5 to the output of the inverting amplifier 3 DC, the third switch 12 - the output of the first trigger 20 to the resistor 7, and the first input to the first input of the ZI element 15 output of the first counter 11. Moreover, the integration process continues with the initial conditions determined by the residual voltage

40

45

50

55

on the first capacitor, 5 UC1 and the residual duration of the feedback pulse, e-d. The overflow of the second counter 18 will occur after a time interval Ј-d-c after the end of the second half period and the first - the trigger 20 will switch to the zero state, which corresponds to the end of the feedback pulse. Thus, despite the fact that the feedback pulse breaks at the moment of switching the switches into two parts f-atf, the total duration remains constant and accurate to a period of the output frequency of the pulse generator 9, which can be chosen sufficiently high. In the second half period the device works in a similar way and

the resistor 7, and the residual voltage is stored on the first capacitor 5

Y / 2

p iCtbijdt C o

Wooi. U0 (C-JJCJ) RC RC

35

25

After the end of the second half-period, the second switch 8 again switches the first capacitor 5 to the output of the inverting amplifier 3 DC, the third switch 12 - the output of the first trigger 20 to the resistor 7, and the first input of the first element ZI 15 receives the single signal output of the first counter 11. Moreover, the integration process continues with the initial conditions determined by the residual voltage

40

45

0

55

on the first capacitor, 5 UC1 and the residual duration of the feedback pulse, e-d. The overflow of the second counter 18 will occur after a time interval Ј-d-c after the end of the second half period and the first - the trigger 20 will switch to the zero state, which corresponds to the end of the feedback pulse. Thus, despite the fact that the feedback pulse breaks at the moment of switching the switches into two parts f-atf, the total duration remains constant and accurate to a period of the output frequency of the pulse generator 9, which can be chosen sufficiently high. In the second half period the device works in a similar way and

the second capacitor 6 remembers the voltage

g

isg Ј J C-Kt) + i0 dt t

- to

uoci rc

Uec ()

RC

In the proposed device, for the full period of operation, the result of measurement, contained in the reversible counter 10, is determined by the expression

t

(k; -K :) mKt) at with

p + tt + L j; n

UpfH U (CH L M I P a ™ -em. Her ("" ive m

Jct n

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Hz

-at

- lR

D t p

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Claims (1)

Since the measurement error does not accumulate, but is determined only by the residual voltages on the first 5 and second 6 capacitors and the residual duration of the feedback pulses generated during the last period, the measurement accuracy increases over several periods of operation. Invention Formula An electricity meter containing a multiplier, the first input of which is connected through the first switch to the first input bus and the second input directly to the second input bus, the control input of the first switch is integrated with the control input of the reversing counter reversal and the control input of the second switch, whose input. connected to the output of an inverting DC amplifier, the input of which is connected to the first output of the resistor, the output of the multiplier, the output of the reference current source and the first plates first and second konden „ five 0 thirty lp 35 The second plates of which are connected to the first and second outputs of the second switch, respectively, are a pulse generator, characterized in that, in order to improve the measurement accuracy by reducing the error from the coincidence of feedback pulses with the switching points of the switches, a third switch is added to it, the threshold element, the first, second and third counters, the first and second triggers, the first and second elements 2I and the first and second elements of the ZI, with the input of the threshold element connected to the output and direct current amplifier, and the output to the counting input of the reversible counter and the first inputs of the first and second elements 2I, the outputs of which are connected to the installation inputs 1 of the first and second triggers, respectively, the outputs of the last with the first and second inputs of the third switch, respectively, output which is connected to the second output of the resistor, and the control input is combined with the control input of the first ne-1 switch, the second and first inputs of the first elements 2I and ZI, respectively, and the direct output of the first counter The inverse output of which is connected to the second and first inputs of the second elements 2I and ZI, respectively, and the input to the output of the pulse generator and the second inputs of the first and second elements of the ZI, the outputs of which are connected to the installation inputs O of the first and second respectively flip-flops, the outputs of which are connected to the third inputs of the first and second ZI elements.