SM0486
(2) The calibrator is designed to test vibration pickups that register in either
the vertical or horizontal position.
You have to determine the type of pickup
being tested and position it according to its orientation axis (vertical or
horizontal).
For vertical operation, place the case on a firm support with the
cover at the top. For horizontal operation, place the case so that when the cover
is removed, the meter panel is vertical and faces in your direction.
Mount the
pickup to be calibrated on the PC1-A exciter table with the rear end of the pickup
away from the operator. The table is provided with four holes tapped for No. 6-32
NC-2 threaded bolts.
Selection of the proper size mounting bolts and table
mounting bolt holes depends on the type of vibration pickup being calibrated.
(3) The preliminaries are over.
You can proceed with the pickup
calibration, using the procedure which follows.
As you read each step of the
procedure, locate the component in Figures 5 and 6.
(a) Connect the voltage output cable of the vibration pickup to the
meter panel by means of the jack marked PICKUP INPUT. Do not connect the vibration
pickup signal voltage output cable to the calibrator jack marked AC OUTPUT. This
jack is used only to measure the voltage output of the calibrator signal generator
during overhaul adjustment of the calibrator itself.
(b) Attach the power cord of the calibrator to an electrical power
source which produces a regulated input of 115-volt, 50-60 cycle, single-phase
(c) Rotate the knob marked AMPLITUDE to the full counterclockwise
position (minimum amplitude) and move the calibrator power switch to the ON
position.
After the pilot lamp lights, move the signal selector switch marked
PICKUP/SIG GEN to PICKUP.
(d) Rotate the amplitude adjustment to an appropriate midpoint between
the arrow and the maximum position and adjust the amplifier gain knob until the
null indicator meter registers a zero reading.
You should not handle the tester
excessively when in use since this can affect the sensitivity readings.
(e) Throw the
signal selector switch to SIG GEN and adjust the
calibrator potentiometer
knob marked MV/IN/SEC MULTIPLY X 10 until the null
indicator dial is zeroed.
(f) Taking care not to disturb the adjustment of the calibrator, throw
the signal switch to its PICKUP position.
The null indicator should remain at
zero. If a zero null indicator reading is not obtained, repeat steps b, c, d, and
e until there is no change in the null indicator reading when the selector switch
is thrown from SIC GEN to PICKUP.
(g) Read and record the vibration pickup sensitivity directly from the
calibrator potentiometer in terms of millivolts per inch per second.
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