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

Page 2
27106T-90
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 insignificant. 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
configuration 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 qualified 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 firmly.
h) Check bearing torque to confirm it is within specifications.
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 flange 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 confirm it is within specification.