Series 641 Air Velocity Transmitter
High Accuracy, Field Selectable Ranges
The Series 641 Air Velocity Transmitter is the ideal instrument for monitoring air flow. This transmitter uses a heated mass flow sensor which allows for precise velocity measurements at various flow rates and temperatures. The 641’s 16 field selectable ranges provides it the versatility to be selected for several air flow applications. The optional LED produces a complete, low-cost solution for local indication of air flow.
NIST CALIBRATION available in Product Configurator.
- Exhaust stack flow monitoring
- Air control in drying processes
- HVAC air velocity measurements
- Fan supply and exhaust tracking
- Clean room fresh air supply
- Ensure proper lab hood exhaust flow rates
Models & Ordering
- Clean air and compatible, non-combustible gases.
- 3% FS Process gas: 32 to 122°F (0 to 50°C); 4% FS Process gas: -40 to 32°F & 122 to 212°F (-40 to 0°C & 50 to 100°C).
- Response Time:
- Flow: 1.5 s to 95% of final value (output filter set to min.).
- Temperature Limits:
- Process: -40 to 212°F (-40 to 100°C). Ambient: 32 to 140°F (0 to 60°C).
- Pressure Limit:
- 100 psi (6.89 bar) maximum.
- Humidity Limit:
- Power Requirements:
- 12 to 35 VDC, 10 to 16 VAC. 1.5 A rating required on supply due to initial power surge drawn by transmitter.
- Output Signal:
- 4 to 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.
- Process Connections:
- 1/2" male NPT.
- Enclosure Rating:
- Designed to meet NEMA 4X (IP66) for non LED models only.
- Mounting Orientation:
- Unit not position sensitive. Probe must be aligned with airflow.
- 12.6 oz (357.2 g).
- Agency Approvals:
- OPTIONAL DISPLAY VERSION:
- 4-1/2 digit 1/2" red LED.
- 1 FPM, 0.01 MPS (10 FPM @ 10,000 and 15,000 FPM ranges).
- 13.3 oz (377 g).
- Ranges from 250 FPM (1.25 MPS) to 15,000 FPM (75 MPS)
- Optional bright LED display
- Easy push button set-up
- Compact housing
- 4 to 20 mA output
- Digital filter for signal damping
|Model Number||Description||Usually Ships*||Price||Order|
|A-156||Flange mounting plate with 1/2" female NPT.||Same Day||$20.00||Order|
|A-158||Split flange mounting. Can be added to any Dwyer® No. 160 standard pitot tube. Cadmium plated steel. Gasket is pattern for mounting holes. Secure flange loosely to tube, adjust tube depth and tighten screws. Gasket of 1/16" Neoprene fits tightly around tube and against duct for leak-proof seal. Nuts, washers included.||Same Day||$17.50||Order|
|A-159||Mounting gland. Versatile adapter slips on any Series 160, 5/16" standard pitot tube made after Dec. 1990. Two-part stainless steel fitting slides over tube and provides permanent, secure mounting. Where duct interior is accessible, use the washers and jam nut supplied. For blind applications or in thicker materials, use model A-156 flange mounting plate. Once tube is adjusted to proper depth and angle, tighten smaller hex bushing to lock position. Graphite bushing inside assures leak-proof seal even at higher temperatures. TFE bushing also available. Note: For full insertion with this fitting, order next longer pitot tube. A-159 mounting gland is used for both duct mounting and flange mounting.||Same Day||$34.50||Order|
|641-LED||Field-upgradeable LED.||1-2 Weeks||$164.00||Order|
Series 641 Air Velocity Transmitter, 6" probe, with LED display.
Air Velocity Transmitter
NIST Certificate of Calibration
Stainless Steel Tag
Product Data Sheet
- We have recently replaced a Dwyer air velocity transmitter (PFS1300204) with a Dwyer Series 641. The new sensor works fine for only a few days and then starts reading almost no flow. These devices are used in an Air Scrubber application (exhaust stack). Is this the right application for the Series 641? I suspect that moisture might be the issue, but I cannot confirm.
- I do not think you are using the 641 series air velocity transmitter in an appropriate application. Any moisture or particulates in the exhaust could be causing damage to the hot wire sensor, leading to the failure. The difference in the sensors is probably why you got longer life out of the PFS series, which unfortunately, is no longer available. The PFS series used a glass filled polyester sensor, which is a little more robust and can with stand the elements a little better. In your specific application, you might take a look at our 641B series which uses a heated mass flow sensor which can be used in dirty air environments.
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