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Model
339A
Section
111
3-37.
Monitor
Output.
3-38.
The
MONITOR
output provides
a
means
of
driving external
equipment
to
permit
a
more
detailed
analysis
of the
signal
being
measured.
Instruments, such
as
an
oscilloscope,
wave
analyzer, or
spectrum
annalyzer
can
be
used
to
determine
the
nature
of the
total
harmonic
distortion
being
measured.
The
monitor
output
level
is
1
V
rms
for
full-scale
meter
deflection.
The
MONITOR
output
is
disabled
when
using
the
OSCillator
LEVEL
FUNCTION.
3-39.
OSCILLATOR OPERATION.
3-40.
Frequency
Selection.
3-41
The
oscillator
frequency
is
determined by
the
setting
of
the
FREQUENCY
and
FREQUENCY
VERNIER
controls.
The
units
and
tenths controls
determine
the
first
and second
digits
of the desired
r
'-r-
v,
_
,
o
t-a
thon rrmltmheri H
v thp
frequency,
inesc
nuiiiL/^ib
range
selected
on
the
multiplier
control.
As
an
exarriple:
to
set
the oscillator
to
a
frequency
of
5.6
kHz;
set
the units
control
to
5,
the tenths control
to
.6,
and
the
multiplier
to
XI
K.
(The
FREQUENCY
VERNIER
should
be
set to
the
CAL
position.)
The
FREQUENCY
VERNIER
provides
continuous
frequency
tuning
between
steps of the tenths
control
to
permit continuous
frequency
selection
from
10
Hz
to
110
kHz.
3-42.
Output
Level.
3-43.
The
oscillator
output
level
is
controlled by the
OSCILLATOR
LEVEL
control
and
LEVEL
vernier.
The
OSCILLATOR LEVEL
control
selects
output
levels
from
3
mV
rms
full-scale to 3
V
rms
full-scale
in
10
dB V
steps
(600
ohm
load).
The
level
vernier varies the
output
level
from
greater
than
3
V
rms
to
less
than
1
m\
rms
(600
ohm
load).
3-44.
OPERATIONAL
VERIFICATION
CHECKS.
3-45.
The
following procedures
are
designed
to test
the
operational
capabilities
of the
Model
339A.
If
so desired,
these
tests
can
be substituted
for the
performance
tests
outlined
in
Section IV
for
incoming
inspection
tests
or
to
check operation
after calibration.
Keep
in
mind
however,
these
tests
check
only
the
operational
capabilities
of the
Models
339
A.
They do no
check
the
performance
accuracy.
If
the
instrument
fails
any
of the
following
tests,
refer
service
to
qualified service
personnel.
3-46.
Preliminary
Procedure.
3-47.
Before connecting
power
to
the
339A, perform
the
following:
a.
Be
certain
that
the
rear
panel
VOLTAGE
SELECTOR
switches
are
set
to
correspond
to
the
available
power
line
voltage
and
that the
proper
fuse
is
installed.
b.
Connect power
to
the
339A
and
turn the
LINE
switch
ON.
c.
Set the
FILTER
switches
off
(out).
d.
Set the
METER RESPONSE
switch
to
NOR-
MAL.
3-48.
OSCILLATOR.
3-49.
This
procedure checks
the
output
level
of the
339A
oscillator for
all
frequency
settings.
Frequency
accuracy
is
not checked.
To
check
the oscillator
proceed
as follows:
a.
Set the
FUNCTION
switch
to
OSCillator
LEVEL.
b.
Set the
INPUT
RANGE
control
to
the
10 volt
range.
c.
Set the
FREQUENCY
controls
fully
counterclock-
wise.
d.
Set the
OSCILLATOR LEVEL
control
and
level
vernier
fully
clockwise.
The
meter should
indicate
more
than
6 volts.
e.
Set the
level
vernier
fully
counterclockwise.
The
meter should
indicate
less
than
2
volts.
f.
Set the
INPUT
RANGE
control
to the
+10
dBm
range
and
adjust the
level
vernier for
a
0
dBm
meter
indication (blue
scale).
g.
While observing
the
meter,
set
the
FREQUENCY
controls
to
each
dial
position.
(Allow
time
for the
meter
reading
to stabilize
at
each
setting.)
The
meter
indication
should not vary
more
than
0.6
dBm
from
the
original
setting.
h.
Set the
FREQUENCY
controls
for a
frequency
of
1
kHz.
i.
Adjust
the
level
vernier for a
meter
indication
0
dBm.
j.
Simultaneously
down-range
the
OSCILLATOR
LEVEL
and
INPUT
RANGE
controls
to the
next lower
range.
The
meter should
indicate 0
dBm.
k.
Repeat
Steps
i
and
j
for
each
position of
the
OSCILLATOR LEVEL
control.
3-50.
AC
VOLTMETER.
3-51.
The
following procedure checks
the
ac voltmeter
functions
and
ranges.
Perform
the
following
steps:
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