The IP65 rating is only achieved if a cable is correctly sealed with the provided gland nut. However, it is important to ensure that the cable is not restricted from breathing when sealing the cable on a low range gauge pressure transmitter. Most pressure transmitters with a range up to 60 bar gauge require a vent to ensure that atmospheric pressure is applied to the reverse side of the pressure sensing diaphragm. To be absolutely sure a pressure transmitter is properly vented it is best to use a cable that incorporates a vent tube.
Some manufacturers will use a special DIN plug that incorporates a side vent which allows air in but keeps moisture out. However it is not always clear in the manufacturer’s literature that this side vent is fitted and also it is very easy to replace the DIN plug at a later date with a variation that does not include a custom side vent which could compromise the vent path.
It is possible to vent between the cores of the cable on higher pressure ranges above a few bar but a vent path cannot be guaranteed especially if there is a tight seal around the gland seal or condensation inside the cable. Low pressure ranges are particular sensitive to atmospheric pressure changes and a vent path that is blocked or is not very responsive could lead to inaccurate pressure readings.
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