Handheld Digital Manometer, Maximum Pressure 200 in wc, Minimum Pressure 0 in wc, Pressure Accuracy +/-0.5 Percent, Process Connection Size 1/8 in, 3/16 in, Process Connection Type Hose Barb, Includes Batteries Yes, Digital Display Features 4 Digit LED, NIST Traceable Certificate No, Series 475, Pressure Units in wc, Auto Power Off Yes, Batteries Required Yes, Battery Type 9V Dwyer(R) 475 Series handheld digital manometer allows you to test air or gas pressure in HVAC systems, laboratory testing, and medical respiratory support equipment. The intrinsically-safe unit measures positive, negative, or differential pressure and air velocity when used with a pitot tube, sold separately.