Series 641 Air Velocity Transmitter

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.

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.

Weight:

12.6 oz (357.2 g).

Agency Approvals:

CE.

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:

13.3 oz (377 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

Approvals

• CE Approval
• RoHS Letter of Compliance

Drawings

• CAD Drawing in format .DWG
• Adobe Reader in format .PDF

Model Chart

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.

Related

Series 641RM

Model 641B

Series AVU

Series 641