477B-1 is a series 477B handheld digital manometer. It is a versatile, hand-held, battery operated manometer. It measures either positive, negative or differential pressures with ±0.10% of full-scale accuracy. A memory function allows storage of up to 40 readings for later recall and a backlight provides auxiliary lighting for hard-to-see locations. Also standard is a hold feature; plus both visual and audible overpressure alarms. Typical applications include lab calibration of other pressure instruments and air velocity/air flow measurements in commercial buildings.