As previously discussed, the purpose of the gain reference signal is to
provide the shaker system operator with a stationary signal of sufficient
duration to permit the shaker system gain adjustment necessary to obtain a
1.0g (peak) at the control accelerometer
3-3.3.1 Set up the sinusoidal
oscillator and servo control equipment for a 1.0g (peak) sine sweep from 2000
to 20 Hz at a logarithmic sweep rate of one octave per minute.
3-3.3.2 Advance the tape using the playback control (without recording) for
one minute of elapsed time. Stop the recorder at the conclusion of one
The tape deck must be left running once it is started (for recording
the gain reference signal) until the end of the sweep. This is done so
that no system input levels need be changed once they are set using the
3-3.3.3 Adjust the
upper frequency limit of the sweep oscillator from 2000 Hz to the frequency
chosen as the gain reference (see paragraph 3-3.1.3
the shaker system with the nominal parameter values used in the preliminary
run (paragraph 3-2.2.1
). Bring the level to 1.0g (peak) at
the gain reference frequency.
3-3.3.5 Place the tape deck in the record mode and record the gain
reference signal and control accelerometer output for one minute.
3-3.3.6 Record all
significant parameter measurements (including tape counter readings) in the
appropriate box on the Tape Data Sheet (Figure 3-3).