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 would cause failure of common level sensors.
The most unfortunate circumstances such as for example 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 would be to obtain the lowest possible susceptibility to contamination or build-up of the pressure sensor by optimizing its design. This is exactly why the typical design of a pressure transmitter with narrow pressure ports isn’t used within level probes because it would have a tendency to clog such applications.
The design of the submersible pressure transmitter and its own pressurised sensor diaphragm is optimised in order to achieve very low susceptibility to contamination. However, continuous operation in soiled media can lead to sticking of dirt particles on the stainless 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 should be completed with caution. Always avoid using sharp or edged tools. Looming 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 due to denting or notching, even though it seems 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 current filling level and, therefore, cannot be considered a trusted measuring instrument any more. Thus, complete replacement of the damaged instrument is absolutely necessary.
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