Studies on Effect of Corrosion for the Selection of Material of Self-Compensated Capacitive Type Liquid Level Sensor

摘要

This work deals with the design of fringe capacitance based non-contact type liquid level sensor employing self-compensation feature. The existing capacitive type sensors require additional compensation to overcome the problem of various stray capacitances, specifically due to atmospheric corrosion. This paper emphasizes on the selection of suitable material to accomplish the self-compensation feature in corrosive environment. Rate of attack of corrosion is studied on Copper (Cu) and Aluminium (Al) samples under drizzling environment. Visual Analysis of SEM images of samples exposed for different durations reveal that Al protects itself from the corrosion. Further, performance evaluation of two sensor units with Cu and Al electrodes under the same drizzling environment beside the respective samples indicate that sensor with Al electrodes facilitates the feature of self-compensation in corrosive environment. Further, the sensor is interfaced with Siemens PLC-S200 for liquid threshold level monitoring.