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(c)
Connect the voltage calibrator
out-
put to the voltmeter input with low-loss,
shield-
ed cable (RG-58/U, RG-59/U or equivalent) less
than three feet in length.
(d) . Set the calibrator
output of 0.001
volt at 400 cps.
(e)
Adjust
the voltmeter
GAIN
control
for a meter
reading of 1.0 on the top scale.
(f)
Secure thelocknut on the GAIN con-
trols
(g)
Check the meter
reading to be sure
it still indicates
1.0
on
the top
scale.
If not,
loosen the locknut
and
repeat
steps
(d),
(e) and
(f).
NOTE
This is à basic
adjustment upon which
all others
depend.
It must be correct.
(h)
Set the voltage calibrator
and volt-
meter
range
selector
switch accordingto
Table
IV.
Adjust the corresponding
control for
full-
scale indication.
These
steps
must
be
followed
in order,
namely,
100
mv
first,
then
10
mv,
then 3 mv.
TABLE
IV
Voltmeter
Voltage
Calibrator
Setting
Adjust for
Range
Full-Scale
Position
Indication
100 MILLIVOLTS
|100 MV Control
B |
0.01 Volt
10 MILLIVOLTS
10 MV
Control
0.003 Volt
3 MILLIVOLTS
3 MV
Control
(i)
Repeat
step
(h) once or twice until
no further adjustments are necessary.
0.1 Volt
(j
Turn the
voltmeter
range
selector
switch to
1 VOLT,
(к)
Set the voltage
calibrator to
1.0
volt.
(1)
Adjust the 1 V, 400cps control (R3)
for full scale indication.
This completes the 400
cps calibration.
(m)
The
accuracy
of all other voltage
ranges may be checked in à similar
manner
by
using the voltage calibrator.
(n)
Disconnect
the voltage
calibrator
from the voltmeter.
(6) 1.0 MC Adjustment
(а)
Set the
controls
on the
frequency
response
generator
(FRG)
and
the
associated
signal generator
for
an
output of approximately
0.001 volt at 400 cps.
(b)
Turn the voltmeter
range selector
to 1 MILLIVOLT.
(c)
Connect the special output cable of
the FRG
to the voltmeter
input terminals.
(d)
Adjust the AMPLITUDE
control of
the signal generator until the voltmeter indicates
0.9 on the top scale.
(e)
Use the FRG
METER
SET
control
to adjust
the
FRG
meter
indicator to one of the
calibrating marks.
(f)
Setthe FRG to 1 mc (this will cause
the FRG
meter
indicator to shift).
Reset the me-
ter indicator,
with the amplitude
control,
to the
same
calibrating mark used in step (e).
(е)
Turn the voltmeter
Н. F, TRIMMER
(C28) for а meter
indication
of 0.9
on
the
top
scale.
(h)
Set the signal generator
to
300 kc
and adjust the signal
generator
AMPLITUDE
control for the same
calibrating mark used
in
step (е).
Note the voltmeter reading.
(i)
If the voltmeter
reading of step (h)
is higherthanthe reading taken at 1 mc
(by more
than 1/2 9), turn the trimmer potentiometer (R48)
counterclockwise
about
20?,
(j
Repeat steps (f) and (g).
(k)
Repeat
Step
(h).
If the voltmeter
reading is still higher than the 1 mc
reading (by
more than 1/296),
repeat step (i) and then
steps
(f) and (g) until the 300 kc reading is within 1/296
of the 1 mc
reading.
NOTE
If the voltmeter
reading is low at 300
kc in step (1),
turnthetrimmer
poten-
tiometer clockwise,
thén proceed
to
steps (f), (g) (h), and (k).
11
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