The model HHP91 is a precision manometer for automotive, HVAC, laboratories and general industrial applications. It is compatible with air or non-corrosive and non-ionized gases and liquids. Eight selectable pressure ranges make it compatible with all measuring systems. The readings are displayed in 15mm high digits. Functions include auto off (after approximately 20 minutes), reading hold/min/max, with push-button recall, and a built in tilt stand. This unit comes complete with a built-in sensor with dual inputs for gage or differential measurements.