Xylem H-375 04101 WIND MONITOR-JR - Manual (Page 11)

Page 2
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.
Accurate wind direction calibration requires a Model 18112
Vane Angle Bench Stand. 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. Orient the base so the junction
box faces due south. Visually align the vane with the
crossmarkings and observe the indicator output. If the vane
position and indicator do not agree within 5°, adjust the poten-
tiometer 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 full scale wind direction signal from the signal
conditioning occurs at 355°. 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 0.986 VDC when the instrument is at 355°. (355°/360° X 1.000
volts = 0.986 volts)
Wind speed calibration is determined by propeller pitch and the
output characteristics of the transducer. Calibration formulas
showing wind speed vs. propeller rpm and output frequency are
included below. Standard accuracy is ± 0.3 m/s (0.6mph). For
greater accuracy, the sensor must be individually calibrated in
comparison 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.
To calibrate wind system electronics using a signal from the
instrument, temporarily remove the propeller and connect an
Anemometer Drive to the propeller shaft. Apply the appropriate
calibration formula to the calibrating motor rpm and adjust the
electronics for the proper value. For example, with the propeller
shaft turning at 3600 rpm adjust an indicator to display 17.6 meters
per second [3600 rpm X 0.00490 (m/s)/rpm =17.6 m/s]
Details on checking bearing torque, which affects wind speed and
direction threshold, appear in the following section.
CALIBRATION FORMULAS
Model 05103 Wind Monitor w / 08234 Propeller
Before installation, connect the instrument to an indicator as
shown in the wiring diagram and check for proper wind speed
and wind direction values. To check wind speed, temporarily
remove the propeller and connect the shaft to an Anemometer
Drive. Details appear in the CALIBRATION section of this manual.
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 GND 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.
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