The Extech HD700 offers 11 selectable units of measurement. This differential Pressure Manometer can serve as a low range/high resolution gauge or provide differential pressure up to 0 to 55.40 in. H2O (inches of water). Max/Min recording and Relative time stamp are useful features, as are HD700's Data Hold and Auto Power Off functions. The 2 psi HD700 also features Zero function for offset correction or measurement and a built-in USB interface.