If the specific 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 is to obtain the lowest possible susceptibility to contamination or build-up of the pressure sensor by optimizing its design. This is exactly why the normal design of a pressure transmitter with narrow pressure ports isn’t used within level probes since it would tend to clog in such applications.
The look 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 may 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 few microns. Therefore, cleaning of the diaphragm should be carried out with caution. Always stay away from sharp or edged tools. Additionally it is strongly advised not to use the popular screwdrivers or pens.
If cleaning of the sensor diaphragm is essential, then rinse it utilizing a weak water jet or clean it carefully using compressed air. Damage of the diaphragm due to 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 inner 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 trusted measuring instrument any more. Thus, complete replacement of the damaged instrument is absolutely necessary.
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