Optimizing piezo-resistive strain gauge characteristics for intelligent strain sensing applications

Abstract

This paper reviews current piezo-resistive characteristics pertaining to conventional and novel piezo-resistive strain transducers. These characteristics govern the performance of the sensor node. In this application, low power consumption, high signal to noise ratio (SNR), sensitivity and resolution in the sensor node are optimized for a distributed sensor network. In this low frequency application at < 100 Hz, it is found that electrical noise can limit the nominal resistance of the strain gauge to be used. By reducing the nominal resistance to lower the SNR, power consumption is increased. Optimization of the nominal resistance for excess noise and other material parameters must take place. Typical values have been used to explore the SNR over a range of resistance values and against frequency. The trade-off is also optimized in the volume and sheet resistance of the piezo-resistive material. Irreversible phenomena such as ageing and material creep are responsible for very low frequency drift (approaching DC) with respect to time and temperature. It is found that this drift is material specific and can be numerically compensated in situ. Maximizing sensitivity of the transducer is desirable to reduce the overhead at the sensor front-end. This overhead is shown to be dependant on gauge factor and the configuration of the strain-sensing circuit. The configuration of the strain-sensing circuit impacts on cost, complexity and SNR.