Capacitive Sensor for Level Measurement in Hopper/Silos - Experimental Evaluation

Hoppers and silos are the integrated part of various industrial processes. Hoppers or silos are used mainly as a temporary storage of the product or by-product from the industrial processes. Level measurement in hoppers is a crucial task due to temperature and dusty environment. Various techniques like optical laser based sensors, ultrasonic sensors, strain gauge based sensors etc. are used for level measurement in the hoppers/silos. But for cement or ash level measurement, due to dusty environment ultrasonic sensors and optical sensors are not advisable. Strain gauge based sensors are also not advisable as it work on the physical deformation of the sensor so it has relatively small life cycle. A non-contact type capacitive sensor design is proposed and experimentally evaluated for level measurement in hopper/silos. The calculation for the non-parallel portion of the hopper is also presented in this work. The present design in free from any parasitic capacitances and the outer metallic body of the hopper is used as shield for the capacitive sensor. The experiments are performed for cement clinkers and fly ash and the results are presented.