HP 339A - Page 21

Model
339A
Section
III
339A DISTORTION
MEASUREMENT SET
PRELIMINARY
ADJUSTMENTS.
a.
Set
the
METER
RESPONSE
switch
to
NORMAL.
b.
Set
the
ANALYZER
INPUT/GND
SELECT
switch to
Distortion
ANaiyzer. (Low
input
connected to chassis ground or
floated as
desired.)
c.
Set
the
FiLTER
switches
as
desired.
d.
Connect
the
339A DISTORTION
MEASUREMENT SET
and the
device to be
tested as
shown.
ANALYZER
ADJUSTMENTS.
e.
Set
the
FUNCTION
switch to
DISTORTION.
f.
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
which
extinguishes
both
indicator lights.
g.
Slowly
adjust
the
FREQUENCY controls
in
the
direction indicated by
the
FREQUENCY
indicator lights. The proper
frequency
range
has
been selected
when both indicator
lights are
extinguished.
h.
Adjust
the
DISTORTION
RANGE
control
to
obtain an
"on-scale"
meter
indication as near full-scale as
possible.
i.
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
the
full-scale
per-cent
figure
on
the DISTORTION
RANGE
control.
Figure
3-3.
Distortion
Measurement
of
an
External
Source.
3-18. Distortion
Measurement of
an
External
Source.
Figure
3-3
shows another
measurement
application.
In
this case
the
Model 339A is
used
to
measure the THD
of a
signal
source. The
figure includes
an
illustration of
the
necesary
equipment
connections
and an
operating
procedure for
making
the measurement.
3-20.
AM
DETECTOR.
3-21.
The Model
339A
includes
an
AM DETECTOR to
permit the user
to measure the total harmonic
distortion
of
a modulation
signal
on an RF carrier.
Equipment
connection
and measurement procedures are similar to
those
outlined
in
Figure
3-3
except the input is
connected
to
the AM
DETECTOR input.
3-22.
VOLTMETER
OPERATION.
3-23. The
following
procedures
outline the
operating
procedures
for
the
various
voltmeter
functions.
3-24.
Normal
Voltmeter
Operation.
3-25. To
use
the
Model
339A as a
normal, true
rms
voltmeter,
proceed as
follows:
a.
Set
the
FUNCTION
switch to
INPUT LEVEL.
b.
Set
the
METER
RESPONSE
switch
to
NOR-
MAL.
c.
Set
the
INPUT/GND
SELECT
switch
to
Distortion
ANaiyzer
(low input
connected
to
chassis
ground
or
floating
as
desired).