Extech hd750 digital differential pressure manometer 5psi extech hd 750 p the extech hd750 differential pressure manometer has a plusmn 5 psi range and eleven selectable units of measure it shows the max min avg recordings and the relative time stamp the functions included are data hold auto power off and the zero function the large lcd display with backlighting helps the user see in low lit areas the meter has a heavy duty double molded housing and a built in usb port the hd70