Series 641RM Air Velocity Transmitter with Remote Probe

For Remotely Mounting Electronic Enclosure

The SERIES 641RM features the same highly accurate heated mass flow sensor as the Series 641, with a remote probe construction. The units 6´ cable which connects the sensing probe with the electronic enclosure allows the enclosure to be mounted where it can be more easily accessed.

Product Applications

  • Exhaust stack flow monitoring
  • Air control in drying processes
  • HVAC air velocity measurements
  • Fan supply and exhaust tracking
  • Clean room ventilation monitoring

Models & Ordering

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Model Description Usually Ships Price Order
641RM-12
Ships: Next Day
Price: $450.00
Air velocity transmitter, without LED display. Next Day $450.00 Order
641RM-12-LED
Ships: Next Day
Price: $580.00
Air velocity transmitter, with LED display. Next Day $580.00 Order

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Specifications

Service:
Clean air and compatible, non-combustible gases.
Accuracy:
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:
Non-Condensing.
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.
Mounting Orientation:
Unit not position sensitive. Probe must be aligned with airflow.
Weight:
13.2 oz (374.26 g).
Cable Length:
6' (1.82 m).
Probe Length:
12" (30.48 cm) standard.
Probe Diameter:
5/16" (0.79 cm).

OPTIONAL DISPLAY VERSION:
Display:
4-1/2 digit 1/2" red LED.
Resolution:
1 FPM, 0.01 MPS (10 FPM @ 10,000 and 15,000 FPM ranges).
Weight:
13.9 oz (394.16 g).

Features

  • 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

Accessories

Model Number Description Usually Ships Price Order
Flange mounting plate with 1/2 A-156 Flange mounting plate with 1/2" female NPT. Next Day $16.25 Order
Split flange. A-158 Split flange. Next Day $13.75 Order
Mounting gland with 1/2 A-159 Mounting gland with 1/2" male NPT. Next Day $28.00 Order
641-LED Field-upgradeable LED. Next Day $130.00 Order

Videos

Model Chart

EXAMPLE
641RM
6
LED
Series 641RM Air Velocity Transmitter, 6" probe, with LED display.
SERIES
641RM
 
 
Air Velocity Transmitter
PROBE LENGTH
 
6
12
18
24
30
36
 
6"
12"
18"
24"
30"
36"
OPTIONS     3
10
15
20
25
30
AT
LED
NIST
ST
3 ft. Cable Length
10 ft. Cable Length
15 ft. Cable Length
20 ft. Cable Length
25 ft. Cable Length
30 ft. Cable Length
Aluminum Tag
LED Display
NIST Certificate of Calibration
Stainless Steel Tag

Product Literature

Manuals

Catalog Pages

Approvals

Drawings

Questions

Question
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.
Answer
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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