Dwyer Handheld Digital Manometer Series 477AVThe Series 477AV Handheld Digital Manometer is now available with pressure and velocity measurements along with a number of other convenient features. The built in air velocity and flow calculations provide accuracy and conserve time and error associated with manual calculations. Also featured on this unit are adjustable zero and span values for calibrating in the field, as well as a damping feature to compensate for the fluctuating of readings.