RU1798726C - Device for measuring harmonic coefficient of output signals of quadripoles - Google Patents

Abstract

The invention relates to a measurement technique, in particular to a technique for measuring non-linear distortion of electrical signals. The purpose of the invention; improved measurement accuracy. The goal is achieved by connecting the control input of the signal driver to the output of the computing unit, the output of the sinusoidal signal generator to the second input of the switch, switching on the four-terminal under study between the switch and the active notch filter, and also calculating the Kg of the signal under study using a certain formula. The device also comprises a rms voltage converter, an ADC, memory registers, a control unit, and an indicator. 1 ill.

Description

The device relates to measuring technique and is intended for measuring the harmonic coefficient (KG) of four-terminal devices, for example, amplifiers for various purposes.

The aim of the invention is to improve the accuracy of measurement.

Structural diagram of the device shown in the drawing.

The device for measuring Kg of the output signals of the four-terminal circuits contains a sinusoidal oscillation generator 1, the output of which is connected to the first input of the switch 2 and through the driver 3 of the given signals to the second input of the switch 2, the output of which is connected to the output of the device, the input of which is connected through an active notch filter 4, the converter 5 of the RMS and ADC 6 is connected to the inputs of the first and second memory registers 7 and 8, respectively. The outputs of memory registers 7 and 8 are connected

respectively, to the first and second information inputs of the computing unit

9. whose output is connected to the indicator

10. The first, second and third outputs of the control unit 11 are connected to the control inputs of the first memory register 7, the second memory register 8 and the switch 2, and the computing unit 9, respectively.

The device operates as follows.

The first cycle, the switch 2 is in the first position and the output sinusoidal signal of the generator 1 is supplied to the output of the device and from it through the device under study to the input of the meter. From the input of the device, the signal under investigation is fed to the input of the active notch filter 4. The notch filter 4 suppresses the first harmonic of the signal. The amplified voltage of the higher harmonics is supplied to the input of the RMS converter 5. output constant voltage

/

WITH

AND

00

N

hO 0

On the other hand, proportional to the harmonic coefficient of the signal under study, the ADC is measured b and, according to the control signal from block 11, the corresponding digital code is recorded in memory register 7 (voltage UBM). .

The second beat. Upon a command from the control unit 11, the switch 2 connects the output of the signal shaper 3 with a given Kg to the input of the four-terminal under study, which is initially set, for example, to 50%. Also, as in the first clock cycle of the device, the ADC output digital code proportional to Kg of the given test signal from the control signal from block 11 is recorded in memory register 8 (voltage 1) vg2).

Third beat. The control signal from the control unit 11 in the computing unit 9 calculates the measured Kg by the formula:

where Ui is the RMS voltage of the first harmonic of the signal;

Kg - the desired value of Kg of the investigated signal.

5 The output signal of the four-terminal under study in the second cycle has an RMS voltage, described by the expression

10

iskz2 and. + K2gi + K2,

gzad

(3)

where Kgzad Kg is the input signal of the quadrupole in the second cycle.

We solve equation (2) and (3) with respect to Ui, equate them with each other, square both sides of the obtained equation, solve the obtained equation with respect to Kgi and take into account the selection of only higher

harmonics of the output signal of the studied four-terminal, we finally get

Kg

T yUЈr1 G

luSrz-uirr.J

where is kzzad. fifty%

Ueri, UBr2 are the rms values (RMS) of the voltages of the higher harmonics, respectively, measured at the output of a four-terminal network when a test signal is supplied with a sinusoidal signal and a signal with a given value of Kg.

Then, based on the obtained value of Kg, a certain digital code is set at the second output of the computing circuit Y, with which the Kg of the output signal of the signal shaper 3 is set equal to the measured plus 0.1 Kg meas, i.e. 10% more than measured.

Next, the first two clock cycles of the device are repeated and the resulting value of Kg is supplied to the indicator 10.

The operation of the device can be implemented with automatic tracking of the change in the measured Kg input signal by cyclically repeating the above clock cycles. Formula (1) is obtained as follows.

The output signal of the studied four-port network in the first cycle of the device has an RMS voltage, described by the expression

UCK31 U1 V 1 + K,

gee

Kg UIVP (1 +) - (4) 0) 25 Ufo-Uirl

where is ueri. UBr2 - RMS voltage of the higher harmonics of the output signal of the four-terminal network, respectively, in the first and second clock cycles of the device.

Expression (4) can be reduced to the form

Kg

35

Mr. yUarl Kgzad / I - ULl

those. takes the form of expression (1). SUMMARY OF THE INVENTION A device for measuring the harmonic coefficient of the output signals of a four-terminal network, comprising a sine wave generator, the output of which is connected via a shaper to the first input of the switch, an active notch filter, a rms converter, and an analog-to-digital converter, the output of which is through parallel included first and second registers for 50 keys respectively to the first and second inputs of the computing unit, the first output which is connected to the indicator input, and a control unit, the first output of which is connected to the control input

55 of the first memory register, the second to the control inputs of the switch and the second memory register, and the third to the control input of the computing unit, characterized in that, in order to increase

the accuracy of the measurement, the output of the sinusoidal oscillator is connected to the second input of the switch, the output of which is connected to the input terminals of the four-port under study, the output terminals of which are connected to the input of the active notch filter, and the control input of the signal driver with the given values of the harmonic coefficient is connected to the second output of the computing unit , and the value of the harmonic coefficient is calculated by the formula

Kg UP | g1 Kgzed Uir2 - U | r1

- /

where UBri, UBr2 are the rms values: the values of the voltages of the higher harmonics, respectively, measured at the output of the four-terminal network when a test signal is supplied with a sinusoidal signal and a signal with a given value of Kg;

Kgzad - set value Kg of the test signal from the output of the driver.