Xylem H-375 04101 WIND MONITOR-JR - Manual (Page 3)

Page 2
INSTALLATION
Proper placement of the instrument is very important. Eddies from
trees, buildings, or other structures can greatly influence wind
speed and wind direction observations. To get meaningful data
for most applications locate the instrument well above or upwind
from obstructions. As a general rule, the air flow around a
structure is disturbed to twice the height of the structure upwind,
six times the height downwind, and up to twice the height of the
structure above ground. For some applications it may not be
practical or necessary to meet these requirements.
FAILURE TO PROPERLY GROUND THE
WIND MONITOR
MAY RESULT IN ERRONEOUS SIGNALS
OR TRANSDUCER DAMAGE.
Grounding the Wind Monitor is vitally important. Without proper
grounding, static electrical charge can build up during certain
atmospheric conditions and discharge through the transducers.
This discharge can cause erroneous signals or transducer
failure. To direct the discharge away from the transducers, the
mounting post assembly is made with a special antistatic plastic.
It is very important that the mounting post be connected to a good
earth ground. There are two ways this may be accomplished.
First, the Wind Monitor may be mounted on a metal pipe which is
connected to earth ground. The mounting pipe should not be
painted where the Wind Monitor is mounted. Towers or masts
set in concrete should be connected to one or more grounding
rods. If it is difficult to ground the mounting post in this manner,
the following method should be used. Inside the junction box the
terminal labeled EARTH GROUND is internally connected to the
antistatic mounting post. This terminal should be connected to an
earth ground (refer to wiring diagram).
Initial installation is most easily done with two people; one to
adjust the instrument position and the other to observe the
indicating device. After initial installation, the instrument can be
removed and returned to its mounting without realigning the vane
since the orientation ring preserves the wind direction refer-
ence. Install the Wind Monitor following these steps:
1. MOUNT WIND MONITOR
a) Place orientation ring on mounting post. Do Not tighten
band clamp yet.
b) Place Wind Monitor on mounting post. Do Not tighten
band clamp yet.
2. CONNECT SENSOR CABLE
a) Refer to wiring diagram located at back of manual.
3. ALIGN VANE
a) Connect instrument to an indicator.
b) Choose a known wind direction reference point on the
horizon.
c ) Sighting down instrument centerline, point nose cone
at reference point on horizon.
d) While holding vane in position, slowly turn base until
indicator shows proper value.
e) Tighten mounting post band clamp.
f ) Engage orientation ring indexing pin in notch at
instrument base.
g) Tighten orientation ring band clamp.
CALIBRATION
The Wind Monitor is fully calibrated before shipment and should
require no adjustments. Recalibration may be necessary after
some maintenance operations. Periodic calibration checks are
desirable and may be necessary where the instrument is used
in programs which require auditing of sensor performance.
To calibrate for wind direction, the following method can yield vane
calibration accuracies of ±5° or better if carefully done. Begin by
connecting the instrument to a signal conditioning circuit which
has some method of indicating wind direction value. This may be
a display which shows wind direction values in angular degrees or
simply a voltmeter monitoring the output. On a large sheet of paper
or cardboard, carefully draw lines, pie fashion, at 45° increments.
Mark these points with degree values; 0°, 45°, 90°.... Center the
instrument mounting base at the centerpoint of the markings with
the junction box facing South (180°). Visually align the vane with
each crossmarking and observe the indicator output. If the vane
position and indicator do not agree within 5°, it may be necessary
to adjust the potentiometer coupling inside the main housing.
Details for making this adjustment appear in the MAINTENANCE,
POTENTIOMETER REPLACEMENT outline, step 7.
It is important to note that while the sensor mechanically rotates
through 360°, the wind direction signal from the signal condition-
ing occurs at 352°. The signal conditioning electronics must be
adjusted accordingly. For example, in a circuit where 0 to 1.000
VDC represents 0° to 360°, the output must be adjusted for 0.978
VDC when the instrument is at 352°. (352°/360° X 1.000 volts =
0.978 volts)
Wind speed calibration is determined by propeller pitch and the
output characteristics of the transducer. Calibration formulas
showing propeller rpm and frequency output vs. wind speed are
included below. Standard accuracy is +/- 0.5m/sec. For greater
accuracy, the device must be individually calibrated in compari-
son with a wind speed standard. Contact the factory or your
supplier to schedule a NIST (National Institute of Standards &
Technology) traceable wind tunnel calibration in our facility.
Details on checking bearing torque, which affects wind speed
and direction threshold, appear in the following section.
CALIBRATION FORMULAS
Model 04101 Wind Monitor-JR
WIND SPEED vs PROPELLER RPM
m/s = 0.00490 x rpm
knots = 0.00952 x rpm
mph = 0.01096 x rpm
km/h = 0.01764 x rpm
WIND SPEED vs OUTPUT FREQUENCY
m/s = 0.0980 x Hz
knots = 0.1904 x Hz
mph = 0.2192 x Hz
km/h = 0.3528 x Hz
MAINTENANCE
Given proper care, the Wind Monitor should provide years of
service. The only components likely to need replacement due to
normal wear are the precision ball bearings and the wind
direction potentiometer. Only a qualified instrument technician
should perform the replacement. If service facilities are not
available, return the instrument to the company. Refer to the
drawings to become familiar with part names and locations. The
asterisk * which appears in the following outlines is a reminder
that maximum torque on all set screws is 80 oz-in.