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SERIES 641B
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AIR VELOCITY TRANSMITTER
Dirty Air Flow Applications
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The Series 641B Air Velocity Transmitter uses a heated mass ow sensor suitable
for dirty air ow applications. It has user-selectable ranges from 250 FPM (1.25 MPS)
to 2000 FPM (10 MPS).
BENEFITS/FEATURES
• Stainless steel sensor suitable for dirty air ow measurement
• Ranges from 250 FPM (1.25 MPS) to 2000 FPM (10 MPS)
• 4-20 mA output
• Digital lter for signal damping
APPLICATIONS
• Exhaust stack ow monitoring
• Air control in drying processes
• HVAC air velocity measurements
• Fan supply and exhaust tracking
• Clean room ventilation monitoring
MODEL CHART
Model Description
641B-4
641B-4-LED
Air velocity transmitter
Air velocity transmitter with LED display
SPECIFICATIONS
Service: Air and compatible, non-combustible gases.
Accuracy: 5% FS process gas: 32 to 122°F (0 to 50°C); 6% FS process gas: -40 to
32°F and 122 to 176°F (-40 to 0°C and 50 to 80°C).
Response Time: Flow: 1.5 s to 95% of nal value (output lter set to minimum).
Temperature Limits: Process: -40 to 176°F (-40 to 80°C); Ambient: 32 to 140°F (0
to 60°C).
Humidity Limit: Non-condensing.
Power Requirements: 12-35 VDC, 10-16 VAC. 1.5 A rating required on supply due
to initial power surge drawn by transmitter.
Output Signal: 4-20 mA, isolated 24 V source, 3- or 4-wire connection.
Output Filter: Selectable 0.5 -15 s.
Loop Resistance: 600 Ω max.
Current Consumption: 300 mA max*.
Electrical Connections: Screw terminal.
Enclosure Rating: Designed to meet NEMA 4X (IP66) for non LED models only.
Mounting Orientation: Unit not position sensitive.
Weight: 12.6 oz (357.2 g).
*A brief current transient exceeding 300 mA may be seen on startup
ACCESSORIES
Model Description
A-155
A-156
Mounting gland with 1/2˝ male NPT tting
Flange mounting plate with 1/2˝ female NPT
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