SU482636A1 - Autocompensation measuring device - Google Patents

Description

The invention relates to the field of measurement technology. Autocompensation measuring devices are known that contain a resistance sensor, a transformer, a compensation resistor, a reohord, an amplifier. Insufficient accuracy and sensitivity of such devices due to the presence of the angular and current errors of the current transformer. An inductance is introduced into the proposed device, connected in series with the primary winding of the transformer, and a capacitor connected in parallel with the inductance circuit - the primary winding of the transformer. This increases the accuracy and sensitivity of the autocompensation measuring device. The drawing shows the schematic diagram of the proposed device. The device contains a resistance sensor I connected in series with inductance 2 and the primary winding of the transformer 3. Parallel to the inductance circuit - the primary winding of the transformer is connected to a capacitor 4. A compensation resistor 5 and a resistor 6 are connected to the secondary current transformer winding. One sensor output 1 is connected to a common secondary point windings of the transformer 3 and resistor 5. Another output of sensor 1 and the slider of a reichord 6 are connected to the input of amplifier 7. A reversible motor 8, mechanically connected to the engine eohorda 6, connected to amplifier 7. With changing resistance value of the sensor 1, caused by a change in the measured parameter varies the voltage drop on it. In this case, an unbalance voltage appears at the input of amplifier 7, and an increased unbalance voltage drives the reversing motor 8 at its output. The motor moves the slider 6 until the voltage drop across the resistor 5 and the slider 6 does not equalize With the new voltage drop on the sensor 1. The voltage unbalance at the input of the amplifier 7 contains two components: in-phase and quadrature. The in-phase component of the imbalance voltage contains a component determined by the current error of the transformer 3 and compensated by the phase-sensitive amplifier 7. The quadratic component is determined mainly by the angular error of the transformer and causes a decrease in the linear zone of the amplifier, increases its insensitivity, and therefore deterioration

TOCMbsm measurement and dynamic characteristics of the device.

Thus, the systematic current error directly determines the device error, and the angle error indirectly. The coefficient of influence of both transformer errors on the device operation accuracy is greater, the greater the ratio of the initial resistance of sensor 1 to its maximum increment, determined by both the measuring range and the sensitivity of the sensor.

In the described device, both errors of the transformer are compensated.

By connecting the capacitor 4 parallel to the primary winding of the transformer, phase matching of the current through sensor 1 and current of the secondary winding of current transformer 3 is achieved, i.e., elimination of the influence of the angular error. The inclusion of inductance 2 in series with transformer 3 leads to an increase in the current of the secondary winding, i.e., to compensation for the current error.

The values of inductance L and capacitance C are determined with sufficient accuracy by the expressions

WITH-

(+ L)

tgOm (+ T,),

where 8, - is the magnitude of the angular error of the transformer;

Rz - reduced to the primary winding the resistance of the secondary circuit of the transformer; g - active primary resistance

transformer windings; a is the angle of loss in the material of the core; (O is the circular frequency of the supply voltage.

Thus, this device allows to eliminate the effect of current transformer errors, improve the measurement accuracy and expand the capabilities of the device.

Subject invention

An autocompensation measuring device containing a resistance sensor, a transformer, a compensation resistor, a rheochord, an amplifier, characterized in that, in order to increase accuracy and sensitivity, an inductance is inserted in series with the transformer primary winding and a capacitor connected in parallel with the inductance chain primary transformer winding.

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