Relative impedance based level sensor

In process industry, different types of level measurements are available with certain advantages and drawbacks. Some of the common methods are differential pressure based level transmitters, ultrasonic level transmitters, bubbler methods, radar level transmitters etc. This paper describes the method of relative impedance based level sensor which is simple for fabrication and its use. The relative impedance based level measurement method uses two sensors. One sensor is reference sensor, which is completely immersed in the liquid under measurement and the other is measurement sensor. The ratio of impedances between reference sensor and measurement sensor is directly proportional to the level. This method nullifies the changes in electrical parameters of liquid like conductivity or dielectric constant. By using ceramics for holding the sensor plates, the sensor can be used for high temperature applications as well as radiation environment. (author)