If the precise pressure sensor design of the submersible pressure transmitter or level probe is selected to measure the filling levels, this often means that the probe is used under environmental requirements which would 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 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. For this reason the normal design of a pressure transmitter with narrow pressure ports isn’t 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 very low susceptibility to contamination. However, Special 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 this stainless steel diaphragm has already been minimised ex factory to just a few microns. Therefore, cleaning of the diaphragm must be completed with caution. Always avoid using sharp or edged tools. Additionally it is strongly advised never 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 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 inner 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 current filling level and, therefore, cannot be considered a reliable measuring instrument any longer. Thus, complete replacement of the damaged instrument is completely necessary.
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