Fast dynamic liquid level sensor based on liquid resistance

Based on the characteristics of liquid resistance, a new transient liquid sensor has been designed by means of ratio measurement. A new AC exciting constant current source is used as excitation source for the sensor, which not only maintains all features of an ideal exciting constant current source in terms of accuracy, disturbance rejection and stability, but also solves the problem arising from the polarization effect by changing the current directions alternatively. Analyzing the influence on the characteristics of liquid resistance under different temperature and medium, the model of the sensor is built and the model parameters are determined. We adopt the single-chip microprocessor as the measuring unit and control unit of the sensor. Both theoretical analysis and experimental results are presented to show the effectiveness of the sensor. Results show that it is sensitive enough to trace the variability of the liquid level.