If the precise pressure sensor design of the submersible pressure transmitter or level probe is selected to gauge the filling levels, this often means that the probe is used under environmental requirements which may cause failure of common level sensors.
The most adverse conditions such as soiled media, abrasive ingredients and sludge when used in wastewater treatment plants, brackish and wastewater tanks as well as digester towers, impose special requirements on the design of a submersible pressure transmitter. One of many requirements on a submersible pressure transmitter would be to have the lowest possible susceptibility to contamination or build-up of the pressure sensor by optimizing its design. This is the reason the typical design of a pressure transmitter with narrow pressure ports is not used within level probes because it would have a tendency to clog such applications.
The design of the submersible pressure transmitter and its own pressurised sensor diaphragm is optimised to experience very low susceptibility to contamination. However, continuous operation in soiled media can lead to sticking of dirt particles on the stainless steel diaphragm. To obtain the highest accuracy and fastest response times in case of level change, the thickness of the stainless steel diaphragm is already minimised ex factory to just a couple microns. Therefore, cleaning of the diaphragm must be carried out with caution. Always avoid using sharp or edged tools. It is also strongly advised never to use the popular screwdrivers or pens.
If cleaning of the sensor diaphragm is essential, then rinse it using a weak water jet or clean it carefully using compressed air. Damage of the diaphragm due to denting or notching, even though it seems to be purely superficial, results in significant losses in the accuracy of level measurement. Challenge of the diaphragm often shifts the zero point of the pressure measurement in the internal electronic measurement system and additionally distorts the output signal linearisation which includes been adjusted ex works to the undamaged diaphragm. Thus, the submersible pressure transmitter with damaged diaphragm generates falsified measurement of the current filling level and, therefore, cannot be considered a trusted measuring instrument any longer. Thus, complete replacement of the damaged instrument is absolutely necessary.
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