If the specific pressure sensor design of the submersible pressure transmitter or level probe is selected to measure the filling levels, this often means that the probe can be used under environmental requirements which may cause failure of common level sensors.
The most unfortunate circumstances such as soiled media, abrasive ingredients and sludge when used in wastewater treatment plants, brackish and wastewater tanks and even digester towers, impose special requirements on the look of a submersible pressure transmitter. Open-minded of many requirements on a submersible pressure transmitter is to have the lowest possible susceptibility to contamination or build-up of the pressure sensor by optimizing its design. That is why the normal design of a pressure transmitter with narrow pressure ports is not used within level probes since it would have a tendency to clog in such applications.
The look of the submersible pressure transmitter and its own pressurised sensor diaphragm is optimised in order to achieve suprisingly low susceptibility to contamination. However, continuous operation in soiled media may lead to sticking of dirt particles on the stainless diaphragm. To get the highest accuracy and fastest response times in case of level change, the thickness of this stainless steel diaphragm is already minimised ex factory to just a few microns. Therefore, cleaning of the diaphragm should be carried out with caution. Always avoid using sharp or edged tools. It is also strongly advised not to use the popular screwdrivers or pens.
If cleaning of the sensor diaphragm is necessary, then rinse it using a weak water jet or clean it carefully using compressed air. Damage of the diaphragm because of denting or notching, even if it appears to be purely superficial, leads to significant losses in the accuracy of level measurement. Deformation 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 existing filling level and, therefore, can’t be considered a reliable measuring instrument any more. Thus, complete replacement of the damaged instrument is absolutely necessary.
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