TPI 645NPT Manometer Pressure features Differential input with + 29 PSI range. Seven units of measure (mbar, kPa, PSI, mmHg, inHg, mH2O, inH2O). Display - 4 digit dual line with backlight. Smooth - Stabilizes display when measuring fluctuating pressures Data Hold - Freezes reading on display. Min / Max - Records Min/Max readings. Auto Off - Conserve battery power.