Xylem H-375 04101 WIND MONITOR-JR - Manual (Page 4)

Page 3
*Max set screw torque 80 oz-in
POTENTIOMETER REPLACEMENT
The potentiometer has a life expectancy of fifty million revolu-
tions. As it becomes worn, the element may begin to produce
noisy signals or become nonlinear. When signal noise or non-
linearity becomes unacceptable, replace the potentiometer. Refer
to exploded view drawing and proceed as follows:
1. REMOVE MAIN HOUSING
a) Unscrew nose cone from main housing.
b) Gently push main housing latch, visible inside front
housing.
c ) While pushing latch, lift main housing up and remove it from
vertical shaft bearing rotor.
2. UNSOLDER TRANSDUCER WIRE
a) Slide junction box cover up, exposing circuit board.
b) Remove screws holding circuit board.
c ) Unsolder three potentiometer wires (white, green, black),
two wind speed coil wires (red, black) and earth ground
wire (gray) from board.
3. REMOVE POTENTIOMETER
a) Loosen set screw on potentiometer coupling and
remove it from potentiometer adjust thumbwheel.
b) Loosen set screw on potentiometer adjust thumbwheel
and remove it from potentiometer shaft extension.
c ) Loosen two set screws at base of transducer assembly
and remove assembly from vertical shaft.
d) Unscrew potentiometer housing from potentiometer
mounting & coil assembly.
e) Push potentiometer out of potentiometer mounting &
coil assembly by applying firm but gentle pressure on
potentiometer shaft extension. Set o-ring aside for
later use.
f ) Loosen set screw on potentiometer shaft extension
and remove it from potentiometer shaft.
4. INSTALL NEW POTENTIOMETER
a) Place potentiometer shaft extension with o-ring on new
potentiometer (Gap 0.040") and tighten set screw*.
Regrease o-ring if necessary.
b) Push new potentiometer into potentiometer mounting & coil
assembly.
c ) Feed potentiometer and coil wires through hole in bottom
of potentiometer housing.
d) Screw potentiometer housing onto potentiometer mounting
& coil assembly.
e) Gently pull transducer wires through bottom of
potentiometer housing to take up any slack. Apply a
small amount of silicone sealant around hole.
f ) Install transducer assembly on vertical shaft allowing
0.5 mm (0.020") clearance from vertical bearing. Tighten
set screws* at bottom of transducer assembly.
g) Place potentiometer adjust thumbwheel on
potentiometer shaft extension and tighten set screw*.
h) Place potentiometer coupling on potentiometer adjust
thumbwheel. Do not tighten set screw yet.
5. RECONNECT TRANSDUCER WIRES
a) Using needle-nose pliers or a paper clip bent to form a
small hook, gently pull transducer wires through hole
in junction box.
b) Solder wires to circuit board according to wiring diagram.
Observe color code.
c ) Secure circuit board in junction box using two screws
removed in step 2b. Do not overtighten.
6. REPLACE MAIN HOUSING
a) Place main housing over vertical shaft bearing rotor.
Be careful to align indexing key and channel in these
two assemblies.
b) Place main housing over vertical shaft bearing rotor
until potentiometer coupling is near top of main housing.
c ) Turn potentiometer adjust thumbwheel until
potentiometer coupling is oriented to engage ridge in
top of main housing. Set screw on potentiometer
coupling should be facing the front opening.
d) With potentiometer coupling properly oriented,
continue pushing main housing onto vertical shaft
bearing rotor until main housing latch locks into position
with a “click”.
7. ALIGN VANE
a) Connect excitation voltage and signal conditioning
electronics to terminal strip according to wiring
diagram.
b) With mounting post held in position so junction box is
facing due south, orient vane to a known angular
reference. Details appear in CALIBRATION section.
c ) Reach in through front of main housing and turn
potentiometer adjust thumbwheel until signal conditioning
system indicates proper value.
d) Tighten set screw* on potentiometer coupling.
8. REPLACE NOSE CONE
a) Screw nose cone into main housing firmly, using only
hand pressure. Be certain threads are properly
engaged to avoid cross-threading.
FLANGE BEARING REPLACEMENT
If anemometer bearings become noisy or wind speed threshold
increases above an acceptable level, bearings may need re-
placement. A rough check of anemometer bearing condition can
be performed by adding an ordinary paper clip (0.5 gm) to the tip
of a propeller blade. Turn the blade with the paper clip to the
"three o'clock" or "nine o'clock" position and gently release it.
Failure to rotate due to the weight of the paper clip indicates
anemometer bearings need replacement. Repeat this test at
different positions to check full bearing rotation. If needed,
bearings are replaced as follows.
1. REMOVE OLD BEARINGS
a) Unscrew nose cone.
b) Loosen set screw on magnet shaft collar and
remove magnet.
c ) Slide propeller shaft out of nose cone assembly.
d) Remove both front and rear bearings from nose cone
assembly. Insert edge of a pocket knife under bearing
flange and lift it out.
2. INSTALL NEW BEARINGS
a) Insert new front and rear bearings into nose cone.
b) Carefully slide propeller shaft thru bearings.
c ) Replace magnet on propeller shaft allowing 0.5 mm
(0.020") clearance from rear bearing.
d) Tighten set screw* on magnet shaft collar.
e) Screw nose cone into main housing until seated. Be
certain threads are properly engaged to avoid
cross-threading.