Dwyer AVUB User Manual

Series AVUB Air Velocity Transmitter

2-1/4

[57.0]

3

-11/32

[85.0]

9-29/64

[240.0]

8

-55/64

[225.0]

51/64

[2.0]

3/4

[19.0]

Specifications - Installation and Operating Instructions

Bulletin AQ-AVUB

The Series AVUB Air Velocity Transmitters from Dwyer Instruments are

suitable for measuring air velocity within a duct and giving a 0 to 10 V linear
output. A typical application would be in a VAV air conditioning system.

The transmitters operate by measuring the heat loss from one of two
sensing elements in the airstream and hence calculating the air velocity.
The special design of these elements makes the transmitter accurate
over the whole air velocity range and gives excellent immunity to drift.

The sensing elements are clad in metal ensuring a long service life and
enabling the sensors to be cleaned easily.

INSTALLATION
Electromagnetic Capability

Series AVUB Air Velocity Transmitters have built in immunity to electrical
interference. However, to achieve full immunity meeting the standards
described below, a screened cable must be used correctly. The cable
screen must be earthed at the enclosure of the controller/power supply
and connected to the screen inside the AVU casing using the procedure
described on the back page. The inside of the transmitter and the
sensing elements near the end of the probe must be protected from
electrostatic discharge at all times.

Attaching the Cable and Cable Screen

The cable gland contains a rubber insert and a plastic insert. Remove
these inserts. Strip back the cable as shown below. Pass the cable
through the gland outer and rubber and plastic inserts. Fold the screen
back over the plastic insert evenly taking care to remove any pieces of
the screen that detach. Feed the cores through into the AVUB and push
the inserts back into the gland noting the orientation of the 3 pipes.
Tighten the gland outer in place. Finally, connect the cores to the
removable 3-way connector.

SPECIFICATIONS
Service: Clean air and compatible, non-combustible gases.
Accuracy: ±8% of full scale.
Response Time (90%): 10 sec (typical).
Temperature Limits: 32 to 104°F (0 to 40°C).
Humidity Limit: 0 to 90% RH, non-condensing.
Power Requirements: 24 VDC or 24 VAC +10% to 15%.
Output Signal: 0 to 10 VDC.
Max. Start Up Current: 60 mA + output current.
Electrical Connections: Screw terminal. Cable gland for 4 to 8 mm wire

(16 gauge wire).

Enclosure Rating: IP67 except sensing point.
Probe Dimensions: 9.45 x .75˝ (240 x 19 mm).
Mounting Orientation: Unit not position sensitive. Probe must be

aligned with airflow.

Weight: 8.8 oz (250 g).

DWYER INSTRUMENTS, INC.

P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360, U.S.A. Fax: [phone] e-mail: [e-mail]

Phone: [phone] www.dwyer-inst.com

Duct Details

The Series AVUB Air Velocity Transmitter will achieve its stated accuracy
when mounted in a long straight circular duct with the sensing elements

0.242 radius in from the duct wall and the view through the large holes
parallel to the flow direction (the flow at a point 0.242 radius in from the wall
is close to the average flow through the whole duct section for a wide range
of flows).

It is recommended that the unit be mounted at least 6.6 feet (2 meters)
downstream of any heating or cooling devices and at least 6 duct­diameters downstream of any bends or other flow disturbances. Deviation
from ideal mounting is likely to reduce stability and accuracy but should not
affect repeatability. In many HVAC applications, simply screwing directly to
the duct and sealing with the gasket supplied will suffice.

CONNECTION DIAGRAM

For 0 to 10 VDC output versions

Output 0 to 10V

0 V

24 VAC or DC

MOUNTING HOLE DETAILS

MAINTENANCE

The transmitter may read low if the sensing elements are very dirty. To
clean the sensing elements, disconnect the transmitter from power and dip
the end of the probe in water and swirl around. If necessary, use detergent
but do not apply force to the elements. Rinse and allow to dry thoroughly
before reconnecting power.

The body is dustproof and should not need cleaning. If cosmetic cleaning
is required, use a damp cloth with water or isopropyl alcohol.

The Series AVUB Air Velocity Transmitters are not field repairable and
should be returned if repair is needed (field repair should not be attempted
and may void warranty). Be sure to include a brief description of the
problem plus any relevant application notes. Contact customer service to
receive a return goods authorization number before shipping.

©Copyright 2014 Dwyer Instruments, Inc. Printed in U.S.A. 4/14 FR# R8-443850-00 Rev. 1

DWYER INSTRUMENTS, INC.

Phone: [phone] www.dwyer-inst.com

P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360, U.S.A. Fax: [phone] e-mail: [e-mail]