Related to the speed of the Pirani is its ability to help you find leaks. Since the gauge is gas sensitive, if you have a leak and you are at base (equilibrium) pressure with the pump running, if you carefully squirt some gas that isn't air over the various seals and welds, when the gas gets to the place where the hole is, the gas will get sucked in, disperse and find its way (very quickly) to the Pirani tube and you will see a deviation (up or down depending on the gas type) in the pressure. It's quick and that's why you need a fast response gauge. A T/C gauge can't do that.
Steve
Created on Saturday, March 10, 2001 9 PM EDT by Steve Hansen