Hydrostatic pressure sensor is an instrument for the measurement of the level or filling height of non flowing fluids. This type of measurement is based on the so called "hydrostatic effect" which describes the weight force of a stationary, in other words non flowing liquid that increases with increasing depth. This means that the measured hydrostatic pressure directly correlates with the filling height of the tank or vessel (Fig 1).
The level transmitter is simply lowered into the tank, and the force of gravity acts on the diaphragm of the sensor, which responds and converts the measurement into an electrical output signal. As a result, the sensor can be installed in tanks or vessels without the need to empty it first.
Due to the simplicity of this measuring method, hydrostatic pressure sensors are used wherever a level measurement in vented tanks or vessels, lakes, rivers or reservoirs is required. In addition, these instruments are frequently used in deep boreholes where a submersible probe is lowered into the ground to measure the water table.
Depending on the application, the level transmitter can also be supplied with additional functions such as a temperature probe or ex-zone approval (JUMO dTRANS p33). In order to prevent the influence of varying liquid temperatures on the accuracy of the measurement results, it is advisable to use a thermal compensator such as the JUMO dTRANS T4. This device measures and compensates for atmospheric pressure changes automatically.