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level is
controlled.
Both
an accelerometer and a velocity
pick-up
can
he
used
as
the
controlling element.
If the
"Function Selector"
is in
position "Auto"
the displacement level
of
the
exciter
is
controlled
below
a pre-set cross-over
frequency
(adjustable
by means
of
the outer knob on the tuning
capacitor spindle) above
which
the
acceleration
level is
controlled.
The
cross-over
is indicated by means
of the white lamp marked
"Accel.", which will
light
whenever
the instrument
is
switched
to
control
the
acceleration
level
of
the
vibration exciter.
"Vel. Gen. Response"
switch
is introduced to
enable
high
frequency com-
pensation of velocity
type
vibration pick-ups.
With the
switch
in position
"Shaped"
the
compensation
network is
connected
in the input circuit
of
the
vibration
meter
amplifier,
the
frequency charac-
teristic of which then
corresponds
to the
curve shown
in Fig.
4.
When
the
switch
is
set
to
position
"Flat" the
frequency
response is flat
from 5 cps
to 2ooo
cps.
"Accel." lamp indicates when the instrument is
switched for acceleration
level
control.
"Vel. Gen. Input" is
a
three-poled
Cannon
receptacle for
connection of a
' 'elocity type
control
pick-up
(o
r
signal generator
coil).
Input impedance
:
Approximately 200
k.Q.
Max. allowable vel. gen.
impedance is
2ooo
Q.
"Accel. Gen. Input" is
similar
to "Vel. Gen. Input", but
should
be used whC'n
the controlling element consists of an accelerometer
with
associated cathode
follower. Input impedance:
Approximately
80
k.Q.
Maximum allowable
output impedance from the
cathode follower is
1500
.Q.
"Oscillator Output" is
a four-poled Cannon
receptacle. The
output should
not be loaded by impedances
smaller
than 10ooo Q.
Correction
8
tdb
6
4
2
0
20
cjs
40
12
v
v
L----"
~
60
80 100
200
400
/
~""'
v
~
L.,...oo
~
600 800 1000 Cfs
2000
Frequency-
,l~#llle
Fig.
4.
Typical
compensation characteristic.
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