Magnehelic Differential Pressure Gauge Indicate low air or gas pressure-positive, negative or Differential, Accurate within 25. 81 Ranges. PHYSICAL DATA Ambient temperature range: 20° to 140° F.* Rated total pressure: -20" Hg. to 15 psig.+ Overpressure: Relief plug opens at approximately 25 psig Connections: 1/8"' NPT female high and low pressure taps duplicated - one pair side and one pair back. Housing: Die cast aluminium. Case and aluminium parts Iridite-dipped to withstand 168-hour salt spray test. Exterior finish is baked dark grey hammerloid. Accuracy: Plus or minus 2% of full scale (3% on - 0 and 4% on - 00 ranges), throughout range at 70°F. Standard accessories: Two 1/8" NPT plugs for duplicate pressure taps, two 1/8" pipe thread to rubber tubing adapter and three flush mounting adapters with screws. (Mounting and snap ring retainer substituted for 3 adapters in MP & HP gauge accessories.)