A Front-End Circuit for Two-Wire Connected Resistive Sensors with a Wire-Resistance Compensation

Area of Science:

• Electrical Engineering
• Sensor Technology
• Instrumentation

Background:

• Remote resistive sensors are crucial in various industrial and scientific applications.
• Traditional sensor circuits are often susceptible to errors introduced by parasitic wire resistances.
• Accurate measurement of sensor resistance is vital for reliable data acquisition.

Purpose of the Study:

• To propose and characterize a novel front-end circuit for two-wire resistive sensors.
• To achieve measurement insensitivity to parasitic wire resistances and their mismatch.
• To ensure high linearity and accuracy in sensor resistance readings.

Main Methods:

• Development of an OpAmp-based current source with square-wave excitation.
• Integration of twin diodes in the feedback path for resistance compensation.
• Implementation of a low-pass filter for DC output voltage generation.
• Experimental validation using a Pt100 thermal sensor with varying wire resistances.

Main Results:

• The proposed circuit provides a DC output voltage directly proportional to sensor resistance.
• Output voltage exhibits minimal sensitivity to wire resistances and their mismatch (0.01-0.03% FSS error).
• The circuit demonstrates excellent linearity (around 0.01% FSS), independent of parasitic resistances.

Conclusions:

• The novel circuit effectively eliminates the impact of wire resistances on sensor measurements.
• This design offers a robust solution for accurate remote resistive sensing.
• The technology is suitable for applications requiring high precision and reliability, such as temperature monitoring.