means, electronic or mechanical (including photocopying), nor may its
contents be communicate d to a third party without prior written
permission of the copyright holder.
The contents are subject to change without prior notice.
Please observe that this manual does not create any legally binding
obligations f or Vaisala towards the customer or end user. All legally
binding commitments and agreements are included exclusively in the
applicable supply contract or Conditions of Sale.
Throughout the manual, important safety considerations are
highlighted as follows:
Warning alerts you to a serious hazard. If you do not read
and follow instructions very carefully at this point, there is
a risk of injury or even death.
Caution warns you of a potential hazard. If you do not read
and follow instructions carefully at this point, the product
could be dama ged or important data could be l ost.
Note highlights important information on using the product.
Chapter 1 ___________________________________________General Information
Product Related Safety
Precautions
The WAA151 Anemometer delivered to you has been tested
for safety and approved as shipped from the factory. Note
the following precautions:
WARNING
CAUTION
Ground the product, and verify outdoor installation
grounding periodically to minimize shock hazard.
Do not modify the unit. Improper modificatio n can damage
the product o r lead to malfunction.
ESD Protection
Electrostatic Discharge (ESD) can cause immediate or latent
damage to electronic circuits. Vaisala products are
adequately protected agains t ESD for their intended use.
However, it is possible to dam a ge the produ ct by deliver i ng
electrostatic discharges when touching, removing, or
inserting any objects inside the equipment housing.
To make sure you are not delivering high static voltages
yourself:
- Handle ESD sensitive components on a properly
grounded and protected ESD w orkbench. When this is
not possible, ground yourse lf to the equipment chassis
before touching the boards. Ground yourself with a wrist
strap and a resistive connection cord. When neither of the
above is possible, touch a cond uctive part of the
equipment chassi s with y our other ha nd befo re to uc hin g
the boards.
- Always hold the boards by the edges and avoid touching
the component contacts.
Regulatory Compliances
The WAA151 com plies with the follow ing performance and
environmental tes t stand ard s:
- Wind tunnel tests per ASTM standard method D5096-96
(for starting threshold, distance constant, transfer
function; refer to Chapter 6, Technical Data on page 25)
- Exploratory vibration test per MIL-STD-167-1
- Humidity tes t per MIL-STD-810E, Method 507.3
- Salt fog test per MIL-STD-810E, Method 509.3
Warranty
For certain prod ucts Vaisala n ormally gives a l imited one
year warranty. Please obser ve that any such warranty may
not be valid in case of damage due to normal wear and tear,
exceptional operating conditions, negligent handling or
installation, or unauthorized modifications. Please see the
applicable supply contract or conditions of sale for details of
the warranty for each product.
This chapter introduces the WAA151 Anemometer features.
Introduction to WAA151 Anemometer
The WAA151 is an optoelectronic, fast-response, lowthreshold anemometer. In the cup wheel it has three lightweight conical cups providing excelle nt linearity over the
entire operating range, up to 75 m/s. Rotated by the wind, a
chopper disc attached to the cup wheel’s shaft cuts an
infrared light beam 14 times per revolution, generating a
pulse train output from a phototransistor.
The output pulse rate can be regarded directly proportional
to wind speed, for example, 246 Hz = 24.6 m/s. For best
available accuracy, however, the characteristic transfer
function should be used, see section Specifications on page
25, to compensate for starting inertia and slight
overspeeding.
The heating element in the s haft tunnel keeps the
temperature of the bearings above the freezing level in cold
climates. Nominally it provides 10 W of heating power. It is
recommended to use a thermosta t switc h in the se nsor cr oss
arm for switching the heating power on below +4 °C.