The Extech PS101-NIST Differential Pressure Manometer measures both gauge and differential pressure in a &plusm; 1 psi range and can store 99 time stamped readings. The device is ideal for use in HVAC, testing pneumatic controls and pressurized equipment in manufacturing, clean rooms and medical equipment, testing and adjuting regulators, positive pressure testing in clean and operating rooms, and boiler installation and gas furnace pressure switch testing.