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DIRECT CURRENT
OUTPUT
AMPLIFIER GAIN
RANGE V RMS
8
the meter lamps. In the "Load On" position,
AC power remains applied, and the amplifier
is connected to the Exciter Head moving coil.
When switching from "Power Off" to "Load
On" the switch must be allowed to remain at
"Power On" for a short time
(>
2 sec.).
A lockable ten-turn potentiometer provides
an internal DC signal for centring the exciter
head so that maximum displacement can be
obtained with AC signals. This control can
also be used to apply a static force for cyclic
fatigue or other studies. Zero amperes DC
corresponds approximately to a dial setting of
5.0.
Note that since the rear panel "Phase" switch
reverses the direction of current through the
moving coil, any standing table deflections
will also be reversed when switching from oo
to 180°.
This is a single-turn potentiometer with an
approximately
logarithmic
characteristic.
Before turning the POWER switch to the
"Power On" position, the AMPLIFIER GAIN
should be put to "Reset". Otherwise an inter-
nal electronic interlock will cause the input
gate to block the input signal and turn on the
CURRENT lamp, preventing possible
ampli-
fier and/or shaker overdrive.
If the interlock is triggered, the AMPLIFIER
GAIN must be turned fully anticlockwise to
the "Reset" position (switch clicks) to reset
the input gates. Similarly when any of the
four protection circuits cause the input gates
to block the input to the amplifier, the ampli-
fier must be "Reset".
A three-position switch located under the
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