Section
IIf
Model
333A/334A
formation about the device under test than the
expression of distortion magnitude alone. Information
obtained from the oscilloscope pattern
is
specific
and
reveals
the
nature
of distortion which sometimes
occurs
at
such low levels that
it
is
difficult to detect
in
the presence
of
hum and
noise.
The impedance
at
the
OUTPUT terminals
is
2000
ohms,
therefore, ca-
pacitive loads greater than
50
pF should
be
avoided
to
maintain the accuracy
of
meter readings.
3-14.
OPERATING PROCEDURES.
3-15.
INSTRUMEN"
TURN-ON.
a
Set the
115-230
VAC switch
to
coincide with the
line
voltage in
we.
Turn switch to ON position.
Pilot lamp
will
glow, indicating application
d
primary power.
3-16.
ADJUSTMENT OF METER MECHANICAL
ZERO.
3-17.
The meter
ia
properly zero-set when the
pointer rests over the zero calibration mark and the
instrument
ie
in
its
normal operating enivronment
and
is
turned
off,
Zero-set the meter
as
follows
to
obtain
maximum accuracy and mechanical stability:,
Turn instrument on and
allow
it
to
operate
for
at
least
20
minutes, to let meter move-
ment reach normal operating temperature.
b.
Turn
instrument off and allow
30
seconde
for
all
capacitors to discharge.
c. Rotate zero adjustment screw clockwise
un-
til
pointer
is
left
of
zero and moving upscale.
d.
Continue rotating screw clockwise; stop when
pointer
ia
exactly
at
zero.
e.
When
pointer
is
exactly over zero, rotate
adjustment screw
slightly
counterclockwise
to
relieve
tension on pointer suspension.
If
pointer moves
aff
zero, repeat steps c
through
e,
but make counterclockwise
rotation
lese.
a.
3-18.
DISTORTION
MEASUREMENT.
e
DO
NOT EXCEED THE INPUT VOLT-
DAMAGING COMPONENTS
ON
A2
BOARD.
AGES
LISTED
BELOW
ro
PREVENT
VOLTMETER FUNCTION
-lV
RANGE AND BELOW, AND
DISTORTION ANALYZER
FUNCTION
-
MAXIMUM
SENSITIVITY.
1.
300
VABOVE
100
HE
2.
50
VABOVE
1
kHz
3-19.
MANUAL MODE.
a.
Turn
instrument on and mechanically
zero
meter according to procedure in
Paragraphs
3-15
and
3-16.
b.
C.
d.
e.
f.
g.
h.
k.
1.
m.
Set NORM-R.
F.
DET. switch to NORM.
Set FUNCTION switch
to SET
LEVEL.
Set MODE switch to MANUAL.
If
fundamental frequency
is
1
kHz
or
greater,
set
HIGH
PASS FILTER switch to
IN.
Set SENSITIVITY selector to
MIN.
position,
and rotate VERNIER control maximum
counterclockwise.
NOTE
The bandwidth of the SENSI-
TMTY selector
is
reduced
in
the
two
extreme
CCW
positions (positions used with
an input
signal
greaterthan
30
V).
Set METER RANGE switch to SET
LEVEL,
and
set
BALANCE
COARSE
and
FINE
con-
trols to center position.
Connect
signal
to
be
measuredto 333A/334A
INPUT terminals.
I
WARNING
1
REMOVE SHORTING
STRAP
BETWEEN
FRAME GROUND
(A
)
AND
CHASSIS
GROUND (
)
TERMINALS ON
FRONT
PANEL INPUT TERMINALS WHEN
MEASURING DISTORTION BETWEEN
TWOPOINTSWHICHAFEDCOFFSET
FROM GROUND POTENTIAL.
Set
SENSITIVITY selector to
obtain
meter
indication greater than
1/3
full
scale.
Adjust SENSITIVITY VERNIERfor
full
scale
meter indication
if
making
distortion
measure-
ment in percent;
if
making distortion measure-
ment
in
dB
adjust SENSITMTY
VERNIER
for
0
dB
meter indication.
NOTE
If
unable to adjust for full scale
or
OdB
indication, (which indicates
input
signal
is
below
0.3
volts),
set METER RANGE selector down-
scale.
Use
this
new
setting
as
the
100'KDor
OdB
SET LEVEL position,
thus making the next range
30%
or
-10
dB,
etc.
Set FREQUENCY RANGE switch and frequency
dial
to fundamental frequency of input
signal.
Set FUNCTION switch to DISTORTION.
Adjust frequency
dial
vernier and BALANCE
COARSE and FINE controls for minimum
3-2
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