• For use with air and compatible combustible gases
  • Measures positive, negative and differential pressures
  • Ranges from 0-1.000 in. w.c. to 0-150 psi
  • Accurate up to ±0.5% F.S. (60 to 78°F)
  • Instant selection from up to nine English/metric units
  • Stores 40 readings in memory for later reference
  • Large easy-to-read 0.4" LCD display includes switchable backlight for great visibility
  • Both audible and visual overpressure alarms
  • Pressure Hysteresis: ±0.1% of full scale
  • Temperature compensated from 32 to 104°F
  • Connections:
    • Two barbed connections for use with 1/8" or 3/16" I.D. tubing
    • Two compression fittings for use with 1/8" I.D. x 1/4" O.D. tubing (477-7-FM & 477-8-FM only)
  • CE, FM Approved


Dwyer 477 Handheld Digital Manometers are packed with features you need to make low pressure measurement and recording faster, easier and more accurate than ever. First, you can instantly select from up to nine of the most widely used pressure units without having to waste time and risk mistakes with tedious conversions. Next, a non-volatile memory function enables storage of up to 40 readings - perfect for HVAC technicians making Pitot tube traverses of airflow readings across a duct. The Dwyer 477 is FM approved intrinsically safe for hazardous locations, Class 1, Div. 1, Group A, B, C, D, T4.

When working in poorly lighted areas, just switch on the handy backlight feature. It automatically shuts itself off after 20 minutes to minimize battery drain. Electronic zeroing means you simply touch a single key to perfectly null out any minor pressure differences. A display HOLD key freezes the current pressure for those all-too-common situations where readings fluctuate. We even included an audible alarm to warn you of overpressure plus a visual alarm also confirms a value has been stored, eliminating the need to observe display during a duct traverse.

The Dwyer 477 is also available in a convenient, all-in-one kit. The small, light and easy to use kit includes a pitot tube, two static pressure tips with magnetic mounting to measure pressure drop across filters, condenser coils, etc. Also includes are rubber tubing, 9V battery, step drill, AV calculator slide rule, and custom fitted carrying case.