Current excitation based improved resistance measurement system for remote sensors

Abstract

Resistive sensors are widely used in the industrial domain in an array of applications. However, remote-located resistive measurement systems face performance degradation due to lead wire resistance. Traditionally, a four-wire (Kelvin) method with direct current excitation is used for remote sensor signal conditioning. However, the measurement range and resolution of the conventional Kelvin bridge are affected by the lead resistance and the biasing voltage of the active components used in the system. Moreover, dc-current excitation-based systems suffer from the issue of thermoelectric offset and other dc nonidealities of the active components used in the circuit. This article proposes a four-wire method based on bipolar current excitation for remotely located resistive sensors. The proposed system introduces a new topology by integrating the remote sensor in a transimpedance amplifier (TIA) configuration to enhance the system’s overall measurement range. In addition, the proposed system introduces an auto-calibration feedback loop to compensate for the mismatch between different circuit components and improve the overall system’s accuracy and robustness. The proposed scheme integrates a single-element resistive sensor and a full-bridge resistive sensor configuration. The prototype is validated for a range of 22.1 Ω–2.1 kΩ for a single-element resistive sensor with a worst case relative error of less than 1.05%. This represents a range extension by a factor of 1.67, as compared to conventional four-wire dc-excited systems. Similarly, the system is tested for full-bridge configuration for ±1. 5% variation in sensor resistance. The proposed system is insensitive to the change in lead resistance in the range of 1–470 Ω