Dwyer Series 478A Differential Pressure Digital Manometer, -4.00 to 4.00"WC Range Handheld meter is used to perform positive, negative, and differential pressure measurements and to set supply pressures, verify pressure switch operation, adjust regulators, check pneumatic systems, and computer peripherals For measuring air and compatible gases Accuracy is + or - 1.5% of full scale Extruded aluminum case provides durability Four-digit LCD displays pressure measurement, zero function nulls minor pressure differences before measuring, min/max display provides comparative data, and display hold retains last reading when the display cannot be seen during testing