What is the best placement of sensor tubes coming from the magnahelic gauge for a downdraft paint booth?
The answer depends on what pressure differential you are trying to measure. If you are measuring cabin pressure compared to building pressure, the high-pressure sensor tube should be mounted in the cabin away from any booth openings. The low-pressure tube should be left open to the shop.
If you want to measure static pressure loss across the pit filter, the high-pressure sensor tube should be mounted in the cabin away from any booth openings, and the low-pressure sensor a few inches below the pit filters.