While simple in their design, they are a very effective technology for a direct visual indication of process fluid level. There are many applications across the industry that require the monitoring of the liquid level and there are many different types of level indicators to fulfill these varying needs. In many situations the fluid is dangerous or the place in which the liquid is stored is of such a nature that it is manually impossible to find the level, making some sort of level indicator imperative.http://www.statessensor.com/level-gauge/