[Bill Baer]

Originally Posted by Adger Smith

I have always wondered if you use a pinch that is open to atmosphere if it is subject to Baro changes.

Well considering that the air pressure on the pressurized side is 80 psi and a change of 1" in the barometer is 0.486 psi it would take a barometer change of 2" to change the pressure differential 1% so while barometric pressure does make a difference it's not a significant one.