SU879480A1 - Converter of voltage increment to period - Google Patents

Description

(54) CONVERTER RESISTANCE ADJUSTMENT DURING THE PERIOD

t

The invention relates to the field of electrical measuring equipment and can be used to create devices for measuring the increment of resistance and non-electric quantities, functionally associated with it.

Devices for measuring the increment of resistance are known, comprising a bridge circuit, an unbalance amplifier, an integrator connected in series, a limiter amplifier, and a time interval sensor, to the outputs of which the control inputs of the keys are connected and the time interval meter p.

The disadvantages of these devices are the complexity of the circuit and the effect of key resistance on the measurement result.

The closest to the technical solution is a converter. The resistance of the resistive bridge in the time interval contains a bridge, a differential amplifier, an output

which is connected to one of the inputs of the comparison unit, and the integrator, the output of the comparison unit is connected to the power supply circuit of the bridge and to the input of the integrator, and the output of the integrator to the other input of the comparison unit 2.

The disadvantage of this device is relatively high accuracy due to the nonlinearity of the conversion, as well as the instability of the constant

to integrator time, which introduces an error in the result of the conversion.

The purpose of the conversion is to increase the accuracy of the conversion.

15

The goal is achieved by the fact that the integrator, the output of which is connected to one of the inputs of the comparator unit, is introduced into the impedance increment converter in the period containing the bridge, the differential amplifier connected to the bridge measuring circuit and forming the feedback pulse and sp

voltage source, the voltage source connected to the diagonal of the bridge power supply The output of which is connected to the input of the integrator, and the control input of the feedback pulse driver is connected to the output of the reference unit.

The drawing shows the functional diagram of the device.

It includes a voltage source 1, a resistive bridge 2, consisting of three constant resistors 3 and a measured resistor 4, the resistance of the constant resistors being equal to the initial resistance value of the measured resistor Rj RQ differential amplifier 5, whose inputs are connected to the measuring diagonal bridge, integrator 6, comparison unit 7, feedback pulse generator 8,

The converter works as follows. As the resistor 4 increases by the value of ULR on the measuring diagonal of bridge 2, a voltage difference appears, which is amplified by amplifier 5,

LY

b is the nominal value of the voltage source 1, the gain of the differential amplifier 5; AR is the increment of the measured resistor 4,

 resistance of resistor 3,

Rn included in series with the measured.

It is then fed to the input of the feedback pulse former 8.

Inverted on resistor 3 overvoltage

and

t-fi

- from 1- V - l

will be applied to the input of the integrator 6, the output of which produces a linearly varying voltage with a speed of UQ / tr, where RC is the integration constant.

After time t. output

P

the voltage of the integrator will reach a certain threshold level, Yc. At this point in time, Comparison Block 7 is triggered and starts the driver 8 for a while. A feedback pulse of duration t, amplitude U. and with a polarity opposite to the polarity DO, is also fed to the input of the integrator. The voltage difference Ua-U will recharge the integrator capacitor 6.

The steady state converter is characterized by the equation

n - p ° uq-

Taking into account the expressions (O, (2) and T. 20 -f O, the transform function is obtained

T

The conversion function of the device is jine-linear and does not depend on the stability of the constant integration, the voltage of the power source of the bridge and the threshold of the comparison unit. As a result, the accuracy of the conversion of the increment of resistance in the period increases.

Claims (2)

Invention Formula An impedance increment converter in a period containing a bridge, a differential amplifier connected to the measuring diagonal of the bridge, an integrator whose output is connected to one of the inputs of the comparison unit, characterized in that, in order to increase the conversion accuracy, a feedback driver and a voltage source, the voltage source being connected to the diagonal of the bridge power supply, the integrator inputs are connected in parallel with a constant resistor forming one arm of the bridge and connected to the last consistently measured with emym resistor forming a second arm of the bridge, differential amplifier output is connected to an input of the feedback pulses, whose output is connected to the input of the integrator, and the control input feedback coupled to an output unit comparing the pulse shaper. Sources of information taken into account in the examination t. USSR Author's Certificate No. 531086, cl. G 01 R 17/10, 1975. 2. USSR author's certificate No. 444325, cl. H 03 K 13/20, 1971 (prototkp).