SU805184A1 - Automatic ac bridge - Google Patents

Description

(54) AC AUTOMATIC BRIDGE

one

The invention relates to electrical measuring equipment, and specifically to devices for measuring impedance parameters.

Automatic AC bridges are known, the balancing of which is based on the use of parametric modulation of adjustable parameters, a measuring circuit. In these instruments, the adjustable parameter of the measuring circuit is initially modulated, and then, depending on the sign of the modulation signal increment at the output of the bridge circuit, the state of the latter is changed, bringing it closer to equilibrium 1.

 The disadvantage of these devices is the reduced speed, due to the need for time spent on modulation.

Closest to the proposed technical essence is. An automatic AC bridge containing a generator, a bridge circuit, modulators, adders, amplifiers, subtraction blocks, an equilibrium detector, a reverse trigger and a reverse counter f2.

The disadvantage of this device is its complexity.

The purpose of the invention is to simplify the device.

This goal is achieved by the fact that an automatic AC bridge containing a generator, a modulator connected to it and a measuring bridge, the output of which is connected to one input through a series-connected adder and converter amplifier. to the other input of the subtracting unit, - an equilibrium detector connected between the output of the subtracting unit and the counting inputs of the reversible counter and the reverse trigger, the output of which is connected to the control input reversibly a counter, coupled to the bridge measuring circuit, introduced a controllable inverter connected between the output

5 of the modulator and one of the inputs of the adder, and the control input of the said inverter is connected to the output of the reverse trigger.

The drawing shows the structure0 on the scheme of the proposed device.

The automatic bridge contains a generator 1, the output of which is connected to a bridge measuring circuit (MID) 2 and modulator 3, adder 4, the KOTOpioro input is connected to the output of MID 2, two transducer amplifiers 5 and 6 connected between the output of the adder 4 and MIC 2 and the inputs subtracting it from block 7 and the equilibrium detector 8 connected between the output of the subtracting unit and the counting inputs of the reversible counter 9, controlling the state of the MIC 2, and the trigger 10 of the reverse controlling the counting direction of the reversible counter 9. Between the output of the modulator 3 and one of sums inputs Ator 4 included controllable inverter 11, a control input connected to the output of the reverse trigger.

The device works in the following way;

Let the bridge measure the MSh1, 2 circuit unbalanced and, therefore, its output signal is large. This signal goes directly to the converter amplifier 6 and (through the adder 4) to the amplifier converter 5. To the other input of the adder 4 through the control: inverter 11, the output signal of the modulator 3, which does not vary in amplitude and phase, is balanced. the output of converter 5 will be less or more than the output of converter of amplifier b / depending on the state in which the trigger 10 of the reverse controls the modulation phase. signal by means of a controlled inverter 11. Subtractive unit 7 isolates the differential signal of amplifiers-converters 5 and b, which then goes to equilibrium detector 8, equilibrium detector sets up trigger 10 in reverse direction before starting balancing, in which the output signal of subtractive unit 7 will negative, and then sends pulses to the reversible counter 9 until MIC 2 is balanced. At the equilibrium point, the output signal of the measuring circuit is small (less than half of the step modulation), therefore adding a modulation signal to the output signal of the MIC 2 g (1 FIVES leads to an increase in the output signal of the adder 4 and the converter-amplifier 5 in any state of the reverse trigger 10. With this is the output of the subtracting unit 7 signal

Q will be positive regardless of the state of trigger 10 of the reverse. Under the action of this signal, the equilibrium detector 8 will periodically change the state of the trigger 10 of the reverse of the reverse, but will not change the state of the reversible counter 9.

Claims (2)

1. Grinevich FB Automatic AC bridges, Novosibirsk, Siberian Branch of the Academy of Sciences of the USSR, 1964, p. 38 2. USSR author's certificate on application 2627556/21, 1978.