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"Scanning Speed Multiplier"
switch controls
the
on-off switching of
the
motor drive for the
automatic frequency sweep.
It
also
allows the
sweep
to
take place
at a
ten times lower
speed
than indicated, by the position
of
the "Scanning
Speed
-
degrees/min"
switch.
"Scanning
Speed -
degrees/min."
switch contains
11
positions, and controls
in
conjunction
with the
"Scanning Speed Multiplier" switch,
the
frequency
sweep speed.
"Compressor Function"
switch controls
the function
of
the
automatic com-
pressor when the "Compres sor
Speed" switch
is in position
"Auto".
The proper
setting
of the
switch
depends upon the frequency
sweep
speed
required by the
various vibration test specification,
and the
expected
magnification factors, Q, of the
specimen
resonances.
When the
switch
is in
position
"Standard"
the
compressor speed
will
automatically
increase with
frequency so
that the distortion of the output
signal
is less than 1
%
for
frequencies
above
10
cps. The
increase in
speed
takes place in
steps:-
.
from
5
to
30
cps
the
compressor speed will be
10
db/sec.
from
30
to
100
cps
the
compressor speed
will be
30
db/sec.
from
100
to
300 cps
the
compressor speed
will
be
100
db/sec.
from 300
from 1ooo
from 3ooo
to 1ooo
cps
the
compressor speed
will be 300
db/sec.
to 3ooo
cps
the
compressor speed
will be 1ooo
db/sec.
to
5ooo cps
the
compressor speed
will be 3ooo
db/sec.
With the
switch
in position
"Fast"
the
compressor speeds given
above
should
be multiplied by
3,
the maximum distortion
of
the
output signal
then being
in the order of 2
%.
If
the
switch
is
set
to "Med.
Q"
a
compressor speed of
10
db/sec.
will be
maintained up to 100
cps.
It then
changes
to 30
db/sec., which
is kept
until the
generator oulput
frequency is
300 cps, etc.
Position
"High
Q"
ensures
the 10
db/sec. speed
to b
e
maintained up to
300 cps; 30
db/sec.
to 1ooo
cps, etc.
"Frequen.ey
Range"
switch allows
the
choice of
two frequency ranges
namely
5-5ooo cps
(normal frequency range
of
the
generator
in this
range the
frequency sweep
is true
logarithmic),
and 5005
to 10ooo
cps
(additional
frequency
range
-
sweep
is not logarithmic).
"Compressor Speed db/sec."
switch controls
the
compressor speed
manually
in
6 steps,
i.
e. a fixed compressor speed of
10,
30, 100, 300, 1ooo
or
3ooo
db/sec. can
be freely
chosen.
When the
switch
is in
positicm
"Auto
"
the
actual compressor speed
will depend upon the
generator output
frequency
and
the position
of
the knob
"Compressor
Function".
"Frequency Scale Adjustment"
controls are
used for
correct adjustment
of
the frequency
scale.
9
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