Dwyer 641B Air Velocity Transmitter


Dwyer Instruments

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  • For use with air and compatible, non-combustible gases
  • Accuracy of up to 5%
  • 1.5 second response time
  • Process temperature limit: -40 to 176°F (-40 to 80°C)
  • Power Requirements:12-35 VDC, 10-16 VAC. 1.5 A rating required on supply due to initial power surge drawn by transmitter
  • 4-20 mA output, isolated 24V source, 3 or 4-wire connection.
  • Output Filter: Selectable 0.5-15 (seconds)
  • Loop Resistance: 600 ohms max
  • Screw terminal electrical connections
  • NEMA 4X (IP66) enclosure

The Dwyer 641B Air Velocity Transmitter uses a heated mass flow sensor technology. It has four user-selectable ranges from 250 FPM to 2000 FPM with four corresponding metric ranges of 1.25 MPS to 10 MPS. The 641 B provides an isolated 4-20 mA output proportional to the velocity.

The Dwyer 641B's steel sensor allows the unit to be used in dirty air environments. This rugged sensor is ideally suited for quick field cleaning from a simple cloth to a pulse of air from an air source. Proper sensor performance can be maintained in these polluted environments by easily removing dust and debris from the sensor which is problematic for Pitot tubes and other flow sensing transmitters.

Dwyer A-156 Mounting Plate
Flange mounting plate with 1/2" female NPT
Dwyer A-155 Cable Gland
Cable gland with 1/2" male NPT fitting


This product can be used in the following applications: