Advertisement
Section
III
Model
339A
3-13.
Turn-On and Warm-Up.
3-14.
Before connecting ac
power
to the
339 A, be
certain
the
rear
panel
voltage
selector
switches
are
set
to
correspond
to the
voltage of the available
power
line
and
that the
proper
fuse
is
installed for
the voltage
selected.
For
rated
measurement
accuracy,
the
339A
should
be
allowed
to
"warm-up"
for
at
least 15
minutes.
3-15.
DISTORTION
MEASUREMENT.
3-16. Distortion
Measurement
Using
the
339A
Internal Oscillator.
3-17.
The Model 339A
Distortion
Measurment
Set
is
designed
to
provide
complete
capability for
measuring
Total
Harmonic
Distortion
by combining an
automatic,
high
resolution distortion
analyzer
and
a
low
distortion
signal
source.
Figure
3-2
illustrates
the
fundamental
application of the
Model
339A.
The
figure
shows
the
equipment
configuration
and
includes
an
operating
procedure
for
making
THD
measurements.
339A
DISTORTION
MEASUREMENT
SET
DEVICE
BEING TESTED
ANALYZER
INPUT
PRELIMINARY
ADJUSTMENTS.
a.
Set the
OSCILLATOR LEVEL
control to
OFF.
b.
Set the
METER RESPONSE
switch
to
NORMal.
c
Set the
ANALYZER INPUT/GND
SELECT
switch
to
Distortion ANalyzer.
(Low
input
connected
to
chassis
ground
or floated as
desired.)
d.
Set
FILTER switches as
desired.
e.
Connect
the
339A
DISTORTION
MEASUREMENT
SET
and
the device
to
be
tested
as
shown.
OSCILLATOR
ADJUSTMENT.
f
Set the
FUNCTION
switch
to
OSCillator
LEVEL
and
adjust the
OSCILLATOR
LEVEL
and
LEVEL
vernier controls
for
the
desired
signal
level
as indicated
on
the
meter
(Change
the
METER
INPUT
RANGE
switch as
necesary
to
obtain the proper
meter
range.)
g.
Set the
FREQUENCY
controls
and
FREQUENCY
VERNIER
for
the desired output frequency.
(Use
a
frequency
counter
if
frequency
is
critical.)
ANALYZER
ADJUSTMENT
h.
Set the
FUNCTION
switch
to
DISTORTION.
i.
Select the proper input
range by
turning the
METER
INPUT
RANGE
control
in
the
direction
indicated by the
INPUT
RANGE
indicator
lights.
The
proper
input
range has
been
selected
when
the
INPUT
RANGE
control
is
set
to
the lowest range
w
ic
extinguishes both
indicator
lights.
j
Adjust
the
DISTORTION
RANGE
control
to
obtain
an
"on-scale"
meter
indication
as near
full-scale
as
possible.
k
Read
the
amount
of total
harmonic
distortion
(THD)
in
dB
by
adding
the
dB
figure
on
the
DISTORTION
RANGE
control
and
the
dB
reading
of
the meter,
or
the
amount
of
THD
in
per-cent
is
indicated
by
the
meter reading (second
or third scale)
relative to
t
e
full-scale
per-cent
figure
on
the
DISTORTION
RANGE
control.
Figure
3-2.
Distortion
Measurement
Using
339A
Internal Oscillator.
Advertisement
