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 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. Genuine 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. For this 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 look of the submersible pressure transmitter and its 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 diaphragm. To get the highest accuracy and fastest response times in case of level change, the thickness of the stainless steel diaphragm has already been minimised ex factory to just a couple microns. Therefore, cleaning of the diaphragm must be completed with caution. Always avoid using sharp or edged tools. Fool is also strongly advised never to use the commonly used 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 because of denting or notching, even though it appears to be purely superficial, results in 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 also 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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