The Dwyer Series 475 Mark III handheld digital manometer is ideal for field calibration, monitoring or trouble shooting HVAC systems, clean rooms or a wide range of other low pressure pneumatic systems. This handy instrument measures positive, negative or differential pressures of air and natural gases in ranges from 1" WC to 150 psi. The manometer is approved and is intrinsically safe for hazardous locations, Class 1, Div.1, Group A, B,C, D, T4. Its simple operation and easy to read digital display make it an indispensable test instrument for the plant engineer, industrial hygienist and HVAC technician. The manometer is housed in a durable extruded aluminum case with its solid state circuitry mounted on a tough fiberglass epoxy circuit board. To meet the most demanding applicat