4.3811.00.000_US-Anemometer-DSP_eng.doc
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021511/10/06
3.1
Selection of installation site
As already described, the ultrasonic anemometer transmits sound packages required to measure
the propagation speed. If these sound packages meet surfaces that reflect sound, they are thrown
back as an
echo
and can may result in
incorrect measurements
under unfavourable conditions.
It is therefore advisable to install the ultrasonic anemometer at a
minimum distance of 1 metre to
objects
in the measuring level
.
In general, wind meters should register wind conditions over a wide area. To obtain comparable
values when measuring the ground wind, measurement should be performed at a height of 10
metres above even and undisrupted terrain. Undisrupted terrain means that the distance between
the wind transmitter and the obstruction should be at least ten times the height of the obstruction (s.
VDI 3786). If it is not possible to comply with this provision, the wind meter should be installed at a
height at which measured values are influenced by obstructions located in the vicinity to the least
possible extent (approx. 6-10 m above the interference level). On flat roofs the anemometer should
be installed in the middle of the roof and not at the edge to thus avoid any preferential directions.
3.2
Installation of anemometer
Proper installation of the ultrasonic anemometer is carried out using a tube socket R1½" (Ø 48.3
mm) and 50 mm in length The inside diameter of the tube socket must be at least 40 mm as the
ultrasonic anemometer is electrically connected to the connector (s. Accessories: connecting cable,
compl.) from below. After connection the ultrasonic anemometer is fitted on the tube or mast
socket. The arm of the sonic transformer marked red must be aligned to north. This allows a
bearing to be taken from an object located to the north, e.g. a building or special geographical
feature, using the sonic transformers of the north / south measurement path.
The instrument is fixed to the shaft with the four Allen screws (AF 4 mm).
3.3
Alignment to north
To align the anemometer, the
arm of the sonic transformer marked red must point to north
(true north). To do so, select a conspicuous feature of the landscape to the north or south with a
compass and turn the mast or anemometer until the opposing arms are aligned in this direction.
The user can also position himself to the north or south at an appropriate distance while another
person turns the anemometer or mast as commanded until the relevant pair of sensor arms are
aligned.
It is recommended using a telescope for this process.
When aligning the instrument to north using a compass, the magnetic variation (= deviation in
direction of compass needle from true north) and local magnetic fields (e.g. iron parts, electric
cables) should be taken into account.
3.4
Cables, cable preparation, connector installation
A prepared connecting cable can be supplied for the ultrasonic anemometer (see Accessories).
If the user wants to procure the cable himself, the cable must have the following properties:
8 cores; 0.5 to 0.75 mm² core cross-section for supply; min. 0.14 mm² core cross-section for data
communications ; max. 8 mm cable diameter, resistant to ultraviolet rays, overall shielding.
The coupling socket (mating connector) is included in the scope of supply. This is placed in the
bottom of the box for shipment.
The pin assignment can be found in these Operating Instructions: see under 3.5 pin assignment.
The cable shield should be connected with the cable clamp
.
