Young Gill Propeller Anemometer Models 27106 - Manual (Page 3)

Page 2
27106-90(E)
CALIBRATION
Calibration is determined by propeller pitch and the output
characteristics of the tach-generator.
Both Model 08274 Expanded Polystyrene Propeller and Model 08254
Carbon Fiber Thermoplastic Propeller have a 29.4 cm/rev pitch. This is
equivalent to 0.0049 m/s per rpm and is accurate to ±1%. Zero offset
is insignifi cant. Formulas for other units of measurement appear on the
calibration chart included with this manual.
The tach-generator output is set at the factory for 500 ±2 mV at 1800
rpm. Check the output by removing the propeller from the anemometer
and coupling an Anemometer Drive to the shaft. Check linearity
by taking measurements at several different speeds. If the tech-
generator is out of calibration it must be replaced. See the following
MAINTENANCE section for details on replacement procedure.
Information on checking bearing and transducer torque, which can
affect propeller threshold, also appear in the MAINTENANCE section.
When the propeller is used for measuring vertical wind component,
users may want to apply a 1.25 multiplier to the output signal. This may
be done numerically in data processing operations or electronically
in the signal conditioning. Using the multiplier brings the anemometer
output signal within ±3% of the cosine response for elevation angles
between -30 and +30 degrees. Since the standard deviation of wind
elevation angle in open terrain rarely exceeds 12 degrees, 98% (2.5
standard deviations) of observations will be within ±30 degrees. Using
the multiplier is NOT necessary when the anemometer is used in a
UVW confi guration with YOUNG Model 26601 UVW Translator.
MAINTENANCE
Replace the tack-generator as follows:
Given proper care, the Gill Propeller Anemometer should provide
years of service. Components are conservatively rated and require
little maintenance. The only parts likely to need replacement due to
normal wear are the precision ball bearings and the tach-generator.
The replacement procedures are best performed in a service facility
and only by qualifi ed technicians. If service facilities are not available,
return the instrument to the factory.
Refer to the accompanying drawings to become familiar with part
names and locations.
PROPELLER
The Model 08274 Expanded Polystyrene (EPS) Propeller can be easily
damaged by careless handling, high winds, hail, or birds. Damage
from these causes is not covered by warranty. If the EPS propeller
is repeatedly damaged, consider using the more durable though
slightly less sensitive Model 08254 Carbon Fiber Thermoplastic (CFT)
Propeller.
FLANGE BEARING REPLACEMENT
If anemometer bearings become noisy or wind speed threshold
increases above an acceptable level, bearings may need replace ment.
Check bearing condition using a Model 18310 Anemometer Bearing
Torque Disk. If, after replacing bearings, the torque is still too high,
check the tach-generator.
Replace bearings as follows:
1. REMOVE OLD BEARINGS
a) Remove propeller from anemometer.
b) Unthread and separate shaft housing assembly from
generator housing.
c) Loosen set screw on shaft collar/coupling disk and remove
from propeller shaft.
d) Slide propeller shaft through both bearings and out of
housing.
e) Pull front bearing dust shield off housing.
f) Using the edge of a pocket knife, gently pry front and rear
bearings out of housing.
2. INSTALL NEW BEARINGS
a) Gently insert front bearing into housing.
b) Push front bearing dust shield back onto housing.
c) Carefully slide propeller shaft through front bearing and into
housing.
d) Slide rear bearing over propeller shaft and gently push it into
housing.
e) Place shaft collar/coupling disk on propeller shaft.
f) Allow 0.010 inch (0.25 mm) end play gap between shaft
collar/coupling disk and bearing.
Tighten set screw (80 oz in, 5600 gm-cm max torque).
9) Thread shaft housing assembly into generator housing.
Tighten fi rmly.
h) Check bearing torque to confi rm it is within specifi cations.
TACH-GENERATOR REPLACEMENT
When the tach-generator output becomes erratic (usually due to
brush failure) or begins to show signs of bearing failure (high torque),
the entire generator assembly should be removed and replaced. If
replacing the tach-generator due to excessive torque make certain it is
indeed caused by a worn tach-generator, not the anemometer fl ange
bearings.
Replace the tach-generator as follows:
1. REMOVE OLD GENERATOR ASSEMBLY
a) Remove propeller from anemometer.
b) Unthread generator housing collar. Pull generator housing
away from sensor connector and generator assembly.
c) Note position of generator wires on sensor connector pins.
Unsolder wires from pins and remove old generator
assembly.
2. INSTALL NEW GENERATOR ASSEMBLY
a) Solder wires from new generator assembly onto proper
sensor connector pins. Verify correct polarity: CCW rotation
produces negative output voltage.
b) Slide generator housing over generator assembly. Firmly
tighten housing collar onto connector threads.
c) Check bearing torque to confi rm it is within specifi cation.