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(b) If it is desired to use one regulation speed only, throughout the
frequency sweep, the speed should be chosen with regard to the
distortion at the lowest test frequency. Recommended combinations
based on a maximum distortion of 1
%
are:-
Lowest Frequency of the
Desired Sweep Range:
Lower than
30 c/c
Above
30 cis
100
c/
s
300
cis
1ooo c/s
3ooo c/s
"Compressor
Speed''
Knob Setting:
10
db/sec.
30 db/sec.
100 db/sec.
300 db/sec.
1ooo
db/
sec.
3ooo
db/sec.
The
"Compressor
Function"
switch should in this case be set to any
position except
"Off".
9. Set "Output Switch" to
"High
Pass
"
.
10. Set "Vel. Gen. Response" to
"
Flat".
(Se
also
"Vel.
Gen. Response" p. 12).
11. Set
"Function
Selector" to "Displ.".
12. Set "Displacement-Velocity Range" to the desired displacement level
range. (If an accelerometer is used as the controlling
element
use the
ranges to the right marked "Accel. Gen.". If the vibration level is
controlled by
me~ms
of a velocity pick-up, the ranges to the left marked
"Vel.
Gen." should be used).
Note: The figures
"0.01", "0.1", "1",
and
"10"
indicate full
scale
meter
deflection peak-to-peak displacement level in inches.
13. Turn the
"Output
Voltage" knob
slowly
clockwise until the compressor
has taken over the
control
of the output voltage.
(This can
be observed
on the instrument meter, the pointer of which
should
be kept below the
5 db mark on the lower meter scale).
14. Turn the knob marked "Displacement- Velocity Level" clockwise
,
until
the instrument meter pointer indicates the desired vibration level.
15. Set
"Meter
Switch" in position
"Oscillator
Voltage".
16. Adjust the
"Output
Voltage" potentiometer so that the maximum output
voltage required from the Oscillator during a complete frequency sweep
is 10 Volts.
(The
scanning of the desired frequency range
should
be
carried
out manually and very slowly).
17. Set "Meter Switch" in position "Vibration Level".
The instrument is now ready for
use,
and the vibration test
can
be
started
by setting the "Scanning Speed Multiplier" switch to the desired position.
18
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