Power Requirements: Internal: (2) 9 V alkaline batteries, included, user replaceable and VL1220 or BR1225 lithium metal battery, installed functional, user replaceable; External: AC adapter 9 VDC, 500 mA.
Battery Life: 30 hours (approx).
Engineering Units: In H2O, psi, in Hg, kPa, mbar, cm H2O, m Hg, and user-defined.