(1) Insert ends of cable assembly into opening
b. Mount the vibration transducer in a horizontal
at side of cover.
position on a surface that can be rotated continuously
at 4 rpm.
(2) Solder ends of cable assembly to terminals
on bobbin assembly. Connect red lead to the (+) ter-
c. Connect output of the audio oscillator to a 40-
minal and white lead to the unmarked terminal. Use
watt power amplifier and connect the output of the
98% lead and 2% silver solder with Nokorode flux.
power amplifier to the vibration transducer. Set the
oscillator for 22 cps and adjust the output of the
(3) Clean the terminals on the bobbin assembly
power amplifier to 10V ac. Make fine adjustments to
thoroughly with a camel's hair brush and hot water.
the voltage until the magnet can be heard hitting its
stops (audible clicking sound), then decrease the
( 4 ) Dry terminals at 160F for 20 minutes.
voltage slightly until the magnet is moving its full
travel at 20 to 22 cps without hitting the stops.
(5) Secure strain relief assembly to cover with
set screw.
d. With
the adjusted voltage applied, rotate the
vibration
transducer at 4 rpm for approximately
e. Place the gasket seal on bobbin and case as-
12 hours
to permit the magnet assembly and magnet
sembly.
sleeve to
burnish properly on all sides.
f. Place cover over the bobbin and case assembly,
e. When the dynamic aging procedure has been
aligning screw holes.
completed, reduce the level of the magnetic charge to
obtain a sensitivity of 60 2 mv/in./sec at 75oF as
g . Coat threads of screws with Kwickheat anti-
described in paragraph 1-93.
freeze compound to prevent breaking screws. Place
a screw and washer in each screw hole in the cover
1-91. VIBRATION TRANSDUCER CALIBRA-
and tighten, using 8 to 9 inch-pounds torque. Par-
TION (MAINTENANCE).
tially tighten one screw, then the opposite screw;
then partially tighten the adjacent screw and its
NOTE
opposite screw. Continue this process until final
torquing of screws is completed.
T h e procedure described in this paragraph
applies only to vibration transducers which
h. Calibrate the magnet assembly as described in
h a v e been overhauled or accidentally de-
energized.
i . If the magnet or sleeve has been replaced,
ducer consists of impressing a strong magnetic field
m e c h a n i c a l l y age the transducer as described in
on the unit with the direction of the field parallel to
the sensitive axis. The impressed magnetic field
must be strong enough to completely saturate the
j. Test the transducer as described in paragraphs
magnet assembly. The magnetic charge is then re-
1-66 through 1-69.
duced to the level required to obtain a sensitivity of
60 2 mv/in./sec at 75oF for the Type 4-128-0101,
k. Clean the exterior of the transducer with methyl
or 105 5 mv/in./sec at 75F for the Type 4-118-
alcohol.
0107. Test equipment required for calibration is
listed in figure 1-41.
sembly or the magnet sleeve has been replaced, the
vibration transducer must be dynamically aged. Dyna-
energize the magnet assembly, proceed as follows:
mic aging consists of vibrating the magnet assembly
using a 20-22 cps, 10V ac power source while slowly
a . Place the assembled vibration transducer in
rotating the vibration transducer to allow the magnet
Magnet Charger Model 2470 on an insulated base.
assembly and magnet sleeve to burnish evenly on all
Center the transducer within the charging coil and
sides. To dynamically age the vibration transducer,
connect the charging coil to the magnet charger.
proceed as follows:
b. Set
the CHARGING VOLTAGE LEVEL switch to
a. Energize the magnet assembly as described in
position
1. Press the ENERGIZE button on the magnet
charger
and wait until the voltmeter indicates approx-
charge at this time.
imately
50 volts. Press CHARGE button.
