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 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 found in wastewater treatment plants, brackish and wastewater tanks as well as digester towers, impose special requirements on the design of a submersible pressure transmitter. Envy of the main requirements on a submersible pressure transmitter would be to obtain the lowest possible susceptibility to contamination or build-up of the pressure sensor by optimizing its design. This is why 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 such applications.
The look of the submersible pressure transmitter and its pressurised sensor diaphragm is optimised to experience suprisingly low susceptibility to contamination. However, continuous operation in soiled media may lead to sticking of dirt particles on the stainless steel 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 few microns. Therefore, cleaning of the diaphragm must be carried out with caution. Always stay away from sharp or edged tools. Additionally it is strongly advised never to use the commonly used screwdrivers or pens.
If cleaning of the sensor diaphragm is necessary, then rinse it utilizing a weak water jet or clean it carefully using compressed air. Damage of the diaphragm because of denting or notching, even though it seems 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 current 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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