SU1492304A1 - Digital power meter - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure the power of signals of direct and low frequency signals of alternating current. The purpose of the invention is to improve accuracy. Instead of a hardware multiplier, the multiplication operation is performed by the integrating push-pull voltage converter 6 in the time interval. Integration is performed over eight time slots. The input signals, proportional to the voltage and current measured, and the reference voltage are integrated. The digital power meter also contains input converters 1 and 2 of voltage and current, respectively, source 3 of reference voltage, first 4 and second 5 switches, control unit 7 and generator 8 of clock pulses. 1 il.

Description

ten

15

 1A9230D

The invention relates to a measurement technique and can be used to measure the power of signals of direct and low frequency signals of alternating current.

The purpose of the invention is to improve the accuracy of power measurement.

The drawing shows a block diagram of a digital power meter.

The digital power meter contains input voltage converters 1 and current 2, reference voltage source 3, two KONtMyTaTopa 4 and 5, integrating a push-pull voltage converter 6 in the time interval (PWI 6), control unit 7 and clock generator 8, and The inputs of the input converters 1 and 2 of the voltage and current are the inputs of the meter, and the outputs are connected to the first and second inputs of the first switch 4, the third input of which is connected to the output of the source 3 of the reference voltage 25 and the first input of the second switch 5, the fourth input of the first switch 4 and the second input of the second switch 5 are connected to a common meter meter, the outputs of the first and second switches 4 and 5 are connected to the inputs of the ПЫВ 6, the output of which is connected to the first input of the control unit 7, the second input of which

for two clocks. integration has the form

(Uo - UJ T, - Considering that T T of

Yar

Those

That (1

and,.

 Tc,

o (i)

(1) found- (2)

As soon as the output voltage of the PIR 6 integrator becomes zero, the switch 4 connects to the first input of the NVC 6 a voltage Uij proportional to the input current, and the switch 5 to the second input of the NVD 6 voltage Un. The third cycle begins, the duration of which is defined as

20

T, 2To - T

After substitution (2) i chayut.,

-)

and.

(1 +

(3)

(3), semi- (4)

thirty

After the end of the third cycle, KOMNfyTaTop 4 supplies the first input of the NVD 6 with the voltage Ue, and the switch 5 connects the second input of the NVD 6 to the common bus. In the fourth cycle, the accumulated interval is read. The cycle ends when the output voltage of the NVC integrator 6 is zero. For the third and fourth is connected to the generator output of 8 clock cycles the process equation

the first and second control outputs are connected to the control inputs of the first 4 and second 5 switches, respectively, and the output is the output of the meter.

Digital power meter works as follows.

The power measurement cycle takes ten clock cycles, To.

In the first cycle, switches 4 and 5 connect the inputs of the NVD 6 to a voltage and, proportional to the input voltage, and DO to the voltage of the source 3 of the reference voltage. During T «TO, NVD 6 integrates the difference of the voltages U - U.

In the second cycle, switches 4 and 5 connect the first input of the NVD 6 to the voltage Uo, and the second connect to the common bus. In the NVD 6, the accumulated interval is read.

The stroke ends at the moment when the voltage of the NVD integrator 6 is zero and the voltage starts to reach zero. The equation

40

transformation has the form

(Uo - and) t - UO-T O

Substituting the value of Tj in (5),

Yar

t - t P + «T - TO (1 - - -gf (5)

Find (6)

45

50

55

In the fifth cycle duration Td 2Tv - T switches 4 and 5 connect the inputs of the NVD 6 to the common bus. Then, when U О and О U Uo, О Uy Uo, the time interval Tq can vary from zero to 2 To.

The sixth and seventh bars are similar to the first and second bars, only here Uy is connected instead. Therefore, the expressions for these two conversion cycles are similar to expressions (I) and (2):

(Uo - and.,) Te, -.Uo Tu

ABOUT

(7)

for two clocks. integration has the form

(Uo - UJ T, - Considering that T T of

HF

Those

That (1

and,.

 Tc,

o (i)

(1) found- (2)

As soon as the output voltage of the PIR 6 integrator becomes zero, the switch 4 connects to the first input of the NVC 6 a voltage Uij proportional to the input current, and the switch 5 to the second input of the NVD 6 voltage Un. The third cycle begins, the duration of which is defined as

T, 2To - T

After substitution (2) i chayut.,

-)

and.

(1 +

(3)

(3), semi- (4)

transformation has the form

(Uo - and) t - UO-T O

Substituting the value of Tj in (5),

Yar

(five)

nahot - t П + «Т - TO (1 - - -gf (6)

In the fifth cycle duration Td 2Tv - T switches 4 and 5 connect the inputs of the NVD 6 to the common bus. Then, when U О and О U Uo, О Uy Uo, the time interval Tq can vary from zero to 2 To.

The sixth and seventh bars are similar to the first and second bars, only here Uy is connected instead. Therefore, the expressions for these two conversion cycles are similar to expressions (I) and (2):

(Uo - and.,) Te, -.Uo Tu

ABOUT

(7)

T To (1 -) - (8)

The eighth and ninth analog cycles are the third and fourth, except that Vf is connected instead of Uij. and the expressions for these two clocks are similar to (3), (4), (5) and (6)

Tg 2To - (9)

Substituting (8) in (9), get

Um

Tj 2T- T T,

(one

+ J) Uo

(ten)

Similar to expression (6),

t - t C1 4 - L: i, i b c, / iiN Te - TO (I + - 77- - -TTTS)

Ue, Uo U In the tenth cycle, as in the fifth, switches 4 and 5 connect the inputs of the NVD 6 to the common bus. Then the time interval T may vary from zero to TO. By folding the left and right sides of the expression (6) and (O separately, get

That 1l

TD 21 ,, (I and .i,

where 2Ts, - is an expression of the average

 power values for

conversion period Thus, by alternating the integration of the input signals and the reference voltage, a value is obtained that is proportional to the average value of the measured power during the conversion time.

0

five

five

0

Digital H: sMepMTejrb power, containing input voltage and current transducers, a reference voltage source, two switches integrating a push-pull voltage transducer in a time interval, a control unit and a clock generator, and the inputs of the input voltage and current transducers are with inputs the meter and the outputs are connected to the first and second inputs of the first switch, the third input of which is connected to the output of the reference voltage source, the output of the integrating push-pull converter connected It is connected to the first input of the control unit, the control outputs of which are connected to the control inputs of the first and second switches, characterized in that, in order to improve accuracy, the first switch has four inputs and the second has two, and the first input of the second switch is connected to the source output the reference voltage, the fourth input of the first switch and the second input of the second switch are connected to a common bus, the outputs of the first and second switches are connected to the first and second inputs of the integrating two-cycle converter averaging over the time interval, a second input 5 of the control terminal podklkni to the output of the clock, and the output is the output of a digital power meter.

Claims (1)

Claim Digital power meter containing input converters 5 voltage and current, a reference voltage source, two switches, integrating a push-pull voltage converter in the time interval, a control unit and a clock generator of ¹⁰ pulses, the inputs of the input voltage and current converters being the meter inputs) and the outputs are wired to the first and second inputs of the first switch , the third input of which is connected to the output of the reference voltage source, the output of the integrating push-pull converter is connected to the first input of the control unit, the control outputs of which They are connected to the control inputs of the first and second switches, characterized in that, in order to increase accuracy, the first switch has four inputs and the second two, the first input of the second switch being connected to the output of the reference voltage source, the fourth input of the first switch and the second input of the second the switches are connected to a common bus, the outputs of the first and second switches are wired to the first and second inputs of the integrating push-pull voltage converter in the time interval, the second input 35 of the control unit is connected to the output of the clock generator, and the output is the output of a digital power meter.