If you intend to measure the degree of a liquid easily and reliably, a lot of people will do this using hydrostatic pressure measurement, e.g. with a submersible pressure transmitter or a so called level probe. The characteristic submersed application implicates a maximum exposure to the encompassing, mainly water-based medium, respectively to ?moisture?.
Exposure isn’t only limited by the wetted elements of the pressure sensor housing, but also to the complete immersed length of the cable. In addition, outside the directly immersed level probe parts, the cable, and in particular the cable end, are often exposed to moisture due to splash water, rain and condensation. This is true not merely during operation, but a lot more during installation and commissioning, or when maintenance or retrofitting is required. Irrespective of the target application, whether in water and wastewater treatment or in tank monitoring, moisture ingress into the cable ends of the submersible pressure transmitter may appear early and irreversibly with insufficient protection measures, and, in virtually all cases, lead to premature failure of the instrument.
The ingress of moisture into the cable outlet and from there on downwards in to the electronics of the level probe should be actively eliminated by preventive actions by an individual. To measure the level with highest accuracy, the varying ambient pressure above the liquid media, which is also ?resting? on the liquid, should be compensated contrary to the hydrostatic pressure acting on the pressure sensor (see article: hydrostatic level measurement).
Ventilation tube
Thus, it really is logical that there is a constant threat of a moisture-related failure due to moisture ingress (both via the ventilation tube and through the actual cable itself) if there are no adequate protective measures. To pay the ambient pressure ?resting? on the media, a ventilation tube runs from the sensor element within the level probe, through the cable and out from the level probe by the end of the cable. Because of capillary action within the ventialation tube used for ambient pressure compensation, moisture may also be transported from the encompassing ambience right down to the sensor.
Thus เกจวัดน้ำยาแอร์refco , but additionally moisture penetrates in to the tube, hence the sensor inside the probe and the electronics around it really is irreparably damaged. This can lead to measurement errors and, in the worst case, even to failure of the level probe. To prevent any premature failure, the ingress of moisture in to the ventilation tube must be completely prevented. Additional protection against moisture penetration through the ventilation tube is provided by fitting an air-permeable, but water-impermeable filter element by the end of the vent tube.
bare wires
Not to be ignored can be the transport of the liquid through high-humidity loads across the only limitedly protected internals of the cable, e.g. across the wires, all the way right down to the submersible pressure transmitter. As a leading manufacturer, WIKA uses appropriate structural design to avoid fluid transport, so far as possible, in to the electronics of the submersible pressure transmitter. Because of molecular diffusion and capillary effects, a guaranteed one-hundred percent protection over the full duration of the submersible pressure transmitter, however, is never achievable.
It is therefore recommended that the cable is always terminated in a waterproof junction box with the appropriate IP protection (e.g. IP65) that is matched to the installation location. If this cable junction box is subjected to weather and varying temperature conditions, it is also recommended to pay attention to a controlled pressure equalisation as a way to prevent the formation of condensation or perspiration water and pumping effects. To address this technical requirement, as an accessory to a submersible pressure transmitter, you’ll be able to order a link box with an integrated air-permeable, water-impermeable membrane.
Ultimately, moisture ingress can occur not only through the exposed end of the cable, but also through mechanical harm to the cable sheath or due to liquid diffusion because of improper chemical resistance of the cable material. In the article ?Selection criteria for preventing moisture-related failures of submersible pressure transmitters or level probes? this failure mode is described in detail.
WIKA offers comprehensive solutions for the hydrostatic-pressure level measurement. For further assistance in selecting the submersible pressure transmitter most suitable for the application, please use our contact form.
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