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[PSUBS-MAILIST] Caisson Gauge
Hi All,
Mr Numpty here.
I kind of know the answer to this already, but i thought someone may be able to clarify my mistake.
I was very pleased when i spotted just the sort of gauge i was after mounted on the back of a sewage tanker. A pressure gauge but one that reads a negative pressure as well as a positive. So it starts at 0 and can go to -1 or +1 bar. Idea was that it would go inside the cabin to monitor internal pressure. (I'd like it to be able to measure a negative pressure as well as i intend to drop the internal pressure to test for penetrator seal leaks).
I was just thinking about mounting it up and ive suddenly realised that its not going to work is it? It must measure the port pressure relative to the ambient pressure, which if i just mount it on a bulkhead will always be the same no matter what the pressure actually is.
I suppose i'd have to make a pressure proof box sealed at surface pressure and pipe the port to the inside of the hull? So its kind of like a caisson gauge.
Just thinking aloud really.
James