Level measurement and transmitters
The accurate measurement of levels is required in industry to maintain the proper fluid levels for safe operation, quality production, or the smooth running of equipment. Various sensor technologies are available for measuring levels in liquid and also in solids. Capacitance level sensors measure the change in capacitance to determine liquid levels. An ultrasonic level sensor emits a sound wave. The liquid level is directly proportional to the time delay between the wave emission and its reflection. Differential pressure sensor uses the difference in pressure between two points in a tank to determine the level. Level sensors mostly have a transmitter integrated that enables them to produce a standard signal of 4 to 20 mA or 0 to 10 V as a level varies.
There are various level transmitters. The following figure shows a hydrostatic level transmitter that is usually immersed in water or some liquid whose level is to be measured: