Numerical control variable-resistance device

Abstract

The invention provides a numerical control variable-resistance device. The numerical control variable-resistance device comprises a first port A, a second port B and a voltage adjusting circuit connected between the first port A and the second port B. The voltage adjusting circuit comprises a standard resistor R, an offset voltage source US and a numerical control voltage source U with the variable output voltage. The offset voltage source US is used for offsetting voltage drop at the two ends of the standard resistor R through a reversal-phase follow circuit (2), wherein one end C of the standard resistor R is connected with the first port A, and the other end D of the standard resistor R is connected with the output end US- of the offset voltage source; the reference ground wire end US+ of the offset voltage source US is connected with the reference ground wire end U+ of the numerical control voltage source U; the output end U- of the numerical control voltage source is connected with the second port B; the output end US- of the offset voltage source US is connected with the reference input end of a digital-to-analogue conversion circuit (3) in the numerical control voltage source to provide the reference end voltage for the numerical control voltage source. The numerical control variable-resistance device has the advantages that the simulation output resistance is stable, the definition is adjustable, and the simulation resistance scope is wide.

Description

technical field [0001] The invention relates to the technical field of industrial control, in particular to a numerically controlled rheostat device. Background technique [0002] With the development of electronic technology, in the field of industrial process control calibration, more and more instruments use numerical control rheostat design to facilitate the application. However, there is a common problem in the current rheostat devices on the instrument: the existing rheostat devices generally need to add a current (voltage) source in the circuit to simulate the resistance characteristics. When simulating near zero resistance, the numerical control current (voltage) ) source output is close to its upper limit value, affected by the stability characteristics of its internal electronic devices, the absolute value of the output signal fluctuation is larger than when it outputs a small signal, resulting in poor stability when simulating a small resistance value. In additio...

AI Technical Summary

Problems solved by technology

However, there is a common problem in the current rheostat devices on the instrument: the existing rheostat devices generally need to add a current (voltage) source in the circuit to simulate the resistance characteristics. When simulating near zero resistance, the numerical control current (voltage) ) The source output is close to its upper limit value, affected by the stability characteristics of its internal electronic devices, the absolute value of the output signal fluctuation is larger than when it outputs a small signal, resulting in poor stability when simulating a small resistance value

In addition, when the output of the digital-to-analog conversion circuit of the existing rheostat is zero, the analog resistance output is not zero resistance, which results in fixed resolution and cannot simulate higher resolution in the range of small resistance values.

In addition, the existing varistors have weak anti-interference ability to high-frequency current noise on the external excitation current, and when the field equipment powered by switching power supply is used, the reading jumps greatly

Existing rheostats have a limited range of simulated resistance values ​​and cannot simulate resistance values ​​from 0 to infinity

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