Improved sensitivity of micro thermal sensor for underwater wall shear stress measurement

Drive current is an important parameter of thermal shear stress sensor. Increasing drive current is helpful for enhancing its sensitivity. However, there must be an allowable drive current for the sake of safe working temperature of the sensor. How to make full use of drive current to increase the sensor’s sensitivity working underwater was studied. If the allowable drive current in still water and the current in stream water are used to drive the sensor in lower and higher shear stress input ranges, respectively, sensitivity of the sensor will be enhanced with the sensor working under a safe temperature. The both currents were separately determined by analyzing I–V characteristic and output voltage-shear stress relationship. We can improve the sensor’s sensitivity from 11.8 to 27.5 mV/Pa when shear stress input was 0.4 Pa.