SU391485A1 - DEVICE FOR MEASURING RESISTANCE OF RESISTORS - Google Patents

Description

one

The invention relates to a measurement technique and can be used in systems for automatically controlling resistances, as well as in measuring instruments of universal and special purposes.

Devices for measuring resistors are known, comprising a stabilized current source connected to the measured element, an integrator for creating a linearly varying voltage, a comparison circuit for voltages and two switches. However, the instability of the output current of the source, which enters into the error of the measurement result, as well as the instability of the response level of the comparison circuit, cause an insufficiently high measurement accuracy.

The proposed device contains an additional stabilized current source, the outputs of both current sources are connected to the switch inputs, and the outputs of the latter are connected in antiphase to the input of the voltage comparison circuit connected to the total width through the measuring element and to the input of the integrator connected to the second comparison circuit input.

This allows for improved measurement accuracy.

The drawing shows the functional diagram of the device for measuring the resistance of resistors.

The device contains an integrator / for creating a linearly varying voltage, stabilized current sources 2 n 3, comparison circuit 4 and switches 5 and 6. The outputs of the current sources are separately connected to the inputs of the switches 5 ii 6, and the outputs 7 and 8 of the switches are anti-phase connected to the input comparison circuits 4 connected via the measured resistor 9 with a total thickness and to the integrator input /, the output of which is connected to another input of the comparison circuit 4.

Sources 2 W. 3 have output currents of opposite directions (for example, the current / 1 of the source 2 is negative and the current / 2 of the source 3 is positive). The switches 5 and 5 are controlled synchronously by the output signals from the comparison circuit 4.

The device works as follows.

The measurement cycle consists of two cycles. In the first cycle of operation, the output of the current source 2 is connected via the switch 5 to the measured resistor 9, and a constant voltage is formed on it, directly proportional to the resistor Rx of this resistor. At the same time, the output of the current source 3 via the switch 6 is connected to the input of the integrator 1. As a result, a linearly varying voltage is formed with a slope proportional to the value / 2 of the source 2 current. at the output of the integrator 7 with the voltage Ue on the resistor 9.

In the second cycle of operation, under the influence of the control signal from the comparison circuit 4, switches 5 and 5 connect the output of current source 2 to the input of integrator /, and the output of current source 3 to resistor 9, and receive a second time interval 4 from the switching moment to the comparison of voltage and Ub. The process then repeats. The time interval is proportional to the value of the measured resistance.

A change in the values of the output currents of the sources of the currents introduces an error that is not proportional to these changes, as in known devices, but much smaller. This error is calculated by the formula

- (°) (1 + 5 /)

where 7 is the relative error;

b / - relative current instability.

The additional measurement error at current fluctuations of one of the sources, for example, ± 2%, does not exceed ± 0.02%.

A synchronous change in the values of currents under the conditions does not introduce additional error in the measurement.

The shift of the levels of operation of the comparison circuit, by means of which time intervals i and 4 are allocated, also does not introduce an additional error in the counting. It is only important that this shift in response levels be constant over the measurement cycle time.

Subject invention

A device for measuring the resistance of resistors, comprising a stabilized current source connected to the measured element, an integrator for creating a linearly varying voltage, a voltage comparison circuit and two switches, characterized in that it contains an additional stabilized source the current, the outputs of both current sources are connected to the switch inputs, and the outputs of the latter are anti-phase connected to the input of the voltage comparison circuit connected to the common black bus Without the measuring element, and to the input of the integrator connected to the second input of the comparison circuit.