Extech hd350 pitot tube anemometer and differential manometer extech hd350 p this handheld extech hd350 pitot tube anemometer and differential manometer measures and displays air velocity speed air flow volume ambient air temperature and gauge differential pressure by means of the very small pilot tube the extech hd350 enables the measurement of air current in cramped places small openings or thin pipe systems the speed measurement is done by means of the differential pressure meth