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A Multiplexable Op-Amp Interface for Accurate Readout of Remote Resistive Sensors
Sanya Kuankid1, Jirapong Jittakort2, Apinan Aurasopon3
1Department of Electrical Engineering and Technology, Faculty of Science and Technology, Nakhon Pathom Rajabhat University, Nakhon Pathom 73000, Thailand.
None:
This paper presents a compact and accurate readout circuit for remote two-wire resistive sensors, based on an inverting operational amplifier with a fixed bias voltage, diode steering, and unidirectional square-wave excitation generated by a microcontroller. The proposed method determines the sensor resistance by directly sampling two steady-state voltage plateaus at the op-amp output during alternating excitation phases. This approach enables fast, lead-wire-insensitive measurements without the need for analog filtering or precise PWM duty-cycle control. The architecture supports sensor array multiplexing via analog switches, allowing scalable, low-power implementation. Experimental results demonstrate a maximum relative error of 0.23% across a wide resistance range (0.5-3.5 kΩ), confirming the method's suitability for low-cost, embedded, and remote sensing applications.
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