The Series 477AV Handheld Digital Manometer Boot Kit is Now Available With Pressure, Flow, and Velocity Measurements Along With a Number of Other Convenient 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 Specifications. The Built-in Air Velocity and Flow Calculations Provide Accuracy and 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 Voltage. 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 and 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. The Series 477AV Features a Menu Structure Outline Printed on the Back of the Aluminum Casing. (Standard Model Shown in Picture).