Series 641RM Air Velocity Transmitter with Remote Probe

For Remotely Mounting Electronic Enclosure

The Series 641RM Air Velocity Transmitter with Remote Probe 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.

NIST CALIBRATION available in Product Configurator.

Product Applications

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

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Models & Ordering

Shipping Information

All shipping times are dependent on product availability at time of shipment.

Although we make every effort to ensure a continuous supply of our products, occasional circumstances may force us to temporarily run out of a product, or have shipping delays. Should this occur, customers will be notified soon after placement of any orders for such products and, if applicable, items will be put on backorder. For orders requiring expedited shipment, our customer service team can be contacted to confirm product availability

Build Your Custom Part. Use our Product Configurator

Model	Description	Usually Ships*	Price	Order
641RM-12 Ships: Next Day Price: $650.00	Air velocity transmitter, without LED display.	Next Day*	$650.00	Order
641RM-12-LED Ships: Next Day Price: $829.00	Air velocity transmitter, with LED display.	Next Day*	$829.00	Order

Can't find what you need? Build Your Custom Part. Use our Product Configurator

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).
Range:: 250 FPM (1.25 MPS) to 15,000 FPM (75 MPS).
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

Output signal conditioning with digital filtering
Install in tight spaces with compact design
Easy setup with on-board buttons

Accessories

Model Number	Description	Usually Ships*	Price	Order
A-156	Flange mounting plate with 1/2" female NPT.	1-2 Weeks	$21.00	Order
A-158	Split flange mounting. Can be added to any Dwyer® No. 160 standard pitot tube. Zinc 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.	Next Day	$18.50	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.	Next Day	$36.25	Order
641-LED	Field-upgradeable LED.	1-2 Weeks	$168.00	Order

Videos

Thermo-Anemometers

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

Instruction Manual

Catalog Pages

Series 641RM Catalog Page

Approvals

RoHS Letter of Compliance

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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