SU868609A1 - Power meter - Google Patents

Description

one

The invention relates to electrical measuring equipment, in particular, to devices for multiplying two voltages in an automatic control system.

Power transmitters are known that contain non-linear elements whose inputs are connected respectively to the bus, the voltage of which is proportional to the voltage of the circuit being measured, and to the bus whose voltage is proportional to the current of the circuit being measured, the outputs of the non-linear elements are connected to the inputs of the subtractor i.

A disadvantage of the known devices is low accuracy and narrow di (range of measured powers.

(It is also known a device containing a voltage transformer, the input of which is connected to the first and second input buses, and the output is connected to the input of the first rectifier, the current transformer whose output is connected to the input bus, and the output is connected to the key input, an amplifier with variable coefficient of hard, condensation - torus G23.

Its disadvantage is the narrow range of measured power as well. non-linearity of the measurement characteristic.

The purpose of the invention is to expand the range of measured power and obtain a linear measurement characteristic.

The goal is achieved by the fact that the power meter containing a voltage transformer

10 whose input is connected to the first and second input buses, and the output is connected to the input of the first switch, the current transformer, the input of which is connected to the input bus, and output 15 via the second rectifier to the input of the key, a variable gain amplifier, a capacitor, are entered analog-to-digital converter (ADC) and additional keys,

20a, the variable gain amplifier is designed as a large-scale amplifier, the output of which is connected to the output bus, and through a capacitor is connected to the combined

25 pins of input resistors, other pins of which are connected to the outputs of the keys, the control inputs of which are connected to the corresponding outputs of the analog-digital converter,

30 input which is connected to the output

the first rectifier, the inputs of the additional switches are connected to the output of the second rectifier, and the resistor values are determined by the formula

n - 1

"VI

R.

where n is the number of the resistor

R is the resistance of the resistor

connected to the older category of cerebral palsy,

The drawing shows a diagram of the device.

The device contains a voltage transformer 1, a first rectifier 2, a current transformer 3, a second rectifier 4, a switch 5, a variable gain amplifier 6, a capacitor 7, an analog-to-digital converter (ADC-B, additional switches 9, input resistors 10 and a feedback resistor 11 of amplifier b with variable gain.

The device works in the following way.

The voltage in the circuit of the measured power is fed to the transformer 1 voltage, from the output of which the transformed voltage is fed to the rectifier 2, and from it already rectified to the ADC 8. Using the ADC 8, the voltage is converted into a binary code, which The A / D converters are fed to the control inputs of keys 5 and 9. Each of the keys 5 and 9 is opened by a voltage corresponding to a logical unit, and closed with a voltage corresponding to a logical zero. With the help of switches 5 and 9, the switch 1 input resistors 10, a large-scale amplifier b. Thus, a certain voltage in the circuit of the measured power corresponds to a certain ADC code 8 and a certain equivalent input resistance, a large-scale amplifier, defined by parallel to the pattern of those resistors 10 that are connected to the open keys 5 and 9, the terminals of the resistors 10 are determined by

-P-1

R

R,

where n is the number of the resistor

R is the resistance of the resistor

surrender to elder

discharge ADC.

Since the gain of the amplifier is 6 is determined by the ratio of the resistance value of the resistor 11, which is constant to the equivalent input resistance, the set of resistor 10 ratings allows to obtain a linear change in the gain of the amplifier 6 with respect to the ADC code 8, and therefore to voltage in the circuit of the measured power. Key Inputs

V. .

5 and 9 are connected to the output of the rectifier 4, which rectifies a voltage proportional to the current in the circuit of the measured power supplied to it from the current transformer 3. Thus, the output of the amplifier 6 produces a voltage proportional to the product of the voltage and current in the (measured power circuit. The capacitance of the capacitor 7, included in the feedback of the amplifier 6, serves to filter the high-frequency component resulting from the transfer of the | Keys 5 and 9. By appropriate selection of the capacitance, the bandwidth of the amplifier 6 is changed, so In order to receive a voltage at its output that reflects either instantaneous or total power in the circuit being measured, ADC 8 converts the voltage in the circuit of the measured power into the code many times during the voltage change period as necessary from the condition of obtaining the accuracy of the conversion the digit code of the ADC 8 and the permissible effect of outdated information.

The construction of a power meter according to the proposed scheme makes it possible to extend the power range measured by the device. In addition, the use of an amplifier, the gain of which varies in accordance with the change in the input resistance using resistors whose nominal values correspond to the binary law, eliminates the nonlinearity of the measurement characteristic, since the power supply voltage of the Scale Amplifier remains constant and optimal throughout the meter.

Claims (2)

1. Volgin L.I. Linear electrical transducers for measuring instruments and systems. M., Soviet Radio, 1971, p. ; 2b8-281. 2. USSR author's certificate №585454, cl. C, 01R 21/00, 1977.