The Dwyer 477B7 Handheld Digital Manometer 0-100 psi, 4-Digit LCD is a versatile, hand-held, battery operated manometer in the range of 0-100 psi. This model measures either positive, negative or differential pressures with ±0.10% of full scale accuracy. The user can select from up to seven common English and metric pressure units. A memory function allows storage of up to 40 readings for later recall and a display backlight provides auxiliary lighting for hard-to-see locations. Also standard are a hold feature, visual and audible overpressure alarms and an aluminum housing to protect the instrument against damage.