Conditioning and transmission module for resistive bridge sensors

Abstract

This paper presents an enhanced conditioning and transmission unit aimed for interfacing resistive bridge sensors with remote data acquisition and control systems. The proposed module uses a simple but reliable communication technique based on a combination between frequency and pulse width modulations. This design, based on two transmission methods, ensures the multiplexing on a single carrier of the information regarding the temperature and the unbalance of a resistive bridge sensor. The circuit is practically implemented around a relaxation oscillator architecture, having a central frequency of operation of 8kHz. The polarization of the sensor is realized with a pair of constant current sources for alleviating the influences introduced by the parasitic resistance of the connection wires but also for reducing the influences of the electrical noise. The immunity against perturbations is also inherently increased by the robust transmission method which allows easy and accurate recovering of the measured signals using a proper receiver structure. Compared with existing solutions, the proposed circuit has an improved architecture which makes it compatible with the implementation in integrated circuits technology for improved linearity, stability and compactness.