CROSS ARM
WAC151
Technical Reference
WAC151-T648en-1.1
25 September 1996
Vaisala 1996
© Vaisala 1996
No part of this manual may be reproduced in any form or by any means,
electronic or mechanical (including photocopying), nor may its contents be
communicated to a third party without prior written permission of the
copyright holder.
The contents of instruction manuals are subject to change without prior notice.
Cross Arm WAC151
WAC151-T648en-1.1 Technical Reference
Contents
1. INTRODUCTION .........................................................................................................1
2. INSTALLATION ..........................................................................................................2
3. TECHNICAL DATA .....................................................................................................3
4. APPENDICES / DRAWINGS .......................................................................................4
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Cross Arm WAC151
Technical Reference WAC151-T648en-1.1
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Cross Arm WAC151
WAC151-T648en-1.1 Technical Reference
1. INTRODUCTION
The WAC151 is a cross arm assembly to support the Vaisala WAA151
Anemometer, WAA251 Heated Anemometer and WAV151 Wind Vane. The
assembly consists of an anodized aluminum tube construction with a mounting
clamp for installation on top of a mast.
A water tight junction box is fitted to the cross arm, including a screw
terminal block for connection of the power and signal cables. Inside the
junction box, there is also a thermostat switch for controlling sensor shaft
heating for the standard '151-series sensors.
The junction box is equipped with four cable glands offering easy way for
earthing different cables. Typically, three cable glands are in use; two for
sensor cables one for signal cables. To ensure accurate wind speed
measurement in extreme winter conditions, WAA251 Heated Anemometer as
well as WHP25 Outdoor Mains Power Supply are recommended. The fourth
gland is reserved for the cable supplying heating power for heated
anemometer system.
It is important to notice that wiring instruction label inside the junction box is
for the standard '151-series sensors. However, when WAC151 is used with
WAA251 Heated Anemometer, small wiring changes are necessary. Please,
refer to the drawing WA35172.
The cross arm is installed in the north-south direction, with the wind vane
pointing to the north. The cross arm supports just one way to fix the sensors to
it ensuring correct assemblage.
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Cross Arm WAC151
Technical Reference WAC151-T648en-1.1
2. INSTALLATION
Figure WA35095 illustrates mounting of the WAC151 to the top of a Ø 60
mm pole mast, with the standard mounting clamp. For installation, follow the
procedure below:
1 Remove the four screws attaching the cover of the WAC151 unit.
Remove the cover.
2 Enter the power and signal cables through the cable glands(s). For better
protection against RF interference, follow the earthing instructions of
the cable shield in drawing WA35095.
3 Do the wiring to the screw terminal block according to the drawing
WA35172. Notice that the factory wiring is for WAA151 & WAV151
sensors. If WAA251 is used with WAV151, 10 kΩ NTC (delivered with
the WAA251) must be used instead of thermostat. Tighten the output
cable gland(s).
4 Carefully reattach the enclosure cover with the four screws.
5 Attach the unit to the top of a pole mast with the mounting clamp.
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Cross Arm WAC151
WAC151-T648en-1.1 Technical Reference
3. TECHNICAL DATA
Type & Function
Cross Arm for Vaisala wind sensors.
Mechanical
Dimensions Junction Box 125 x 80 x 57 mm3
Cross Arm length 800 mm
Mounting To a pole mast with a nominal outside
diameter 60 mm. The cross-arm supports the
WAA151, WAA251 and WAV151 sensors.
Material Cross Arm Al, anodized
Junction Box Al, painted
Weight 1.5 kg (without sensors)
Electrical connections
Cable entries Line cable entry through a gland (for cable
diam. 7...10mm) with coaxial connectability
of the cable screen, for proper RF shielding.
Sensor cables enter through two rubber
glands.
I/O connectors Screw terminal connectors (15 pcs) for the
sensors and power lines.
Thermostat switch connects at + 4°C (+3°C)
disconnects at +11°C (+3°C)
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Cross Arm WAC151
Technical Reference WAC151-T648en-1.1
4. APPENDICES / DRAWINGS
WA35095 WAC151 Cross Arm Assembly
ZZ45037 Sensor Wind Vane Cable Assembly
ZZ45036 Sensor Anemometer Cable Assembly
WA35172 WAT11 Wind Sensor Control Unit Basic Wiring (Options)
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