The Dwyer 477AV Handheld Digital Manometer is available with pressure, flow, and velocity measurements along with a number of other features. The 477AV uses a highly accurate differential pressure sensor to offer ± 0.5% full scale accuracy. It displays negative, positive, and differential pressure. For pressure, flow, and velocity there are selectable English and metric units, as seen in the model chart below. The built-in air velocity and volumetric flow calculations conserve time associated with cumbersome manual calculations. Additionally, up to 40 readings can be saved—perfect for HVAC technicians making Pitot tube traverses of airflow readings across a duct. The accuracy that the 477AV Series provides is critical to maintenance personnel and technicians who require a highly accurate standard to check their instrumentation or equipment, to ensure proper performance.

The digital display offers a backlight feature for easier viewing in darker areas. Meanwhile, battery conservation is monitored and displayed in the event of low battery condition. The digital manometer will automatically shut off after 20 minutes to prevent battery drain. This shut-off time can be reduced or disabled if desired. Series 477AV can be field-calibrated by setting zero & span values. Furthermore, the damping feature compensates for the fluctuating readings by averaging input values to display a more stable readout. Included is an audible and visual alarm to warn over flow, over pressure or over velocity.

Displaying Pressure, Velocity, and Flow

The instrument measures pressure using a piezoelectric sensor. When the 477AV is powered on the pressure value and the unit of measurement will be shown. If you select the velocity or flow mode, then velocity or flow will be displayed instead. The mode selection will persist even after the instrument is turned off. In velocity and flow modes, if the reading exceeds 9,999, then a "K" will be displayed next to the unit of measurement and the display will read in units of 1,000 times the original unit of measurement.
 

The 477AV is available in in several pressure ranges. The chart below provides an overview of each.