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Model
3455A
Section
V
SECTION
V
ADJUSTMENTS
S-1.
INTRODUCTION.
S-2.
This
section
contains
complete adjustment
procedures
for
the
Model
34S5A
Digital
Voltmeter. After the
instru-
ment
is
adjusted according
to
the procedures
given
in
this
section,
it
should
meet
the
24-hour accuracy
specifications
listed in
Table
1-1.
5-
3.
EQUIPMENT
REQUIRED.
S4. The
test
equipment
required
for the
adjustments
is
listed at
the
beginning
of
each adjustment procedure
and
in
the
Recommended
Test
Equipment
table
in
Section
I.
If
the
recommended
equipment
is
not
available,
use sub-
stitute
equipment
that
meets
the
critical
specifications
given
in
the
table.
6-
5.
ADJUSTMENT
INTERVAL.
5-6.
The
3455A
adjustments should be
performed
at
90-
day
or
6-month
intervals
depending
on
the
environmental
conditions
and your
specific
accuracy requirements.
Adjust-
ments
should
also
be performed
after
the
instrument has
been
repeaired.
5-7.
ADJUSTMENT
SEQUENCE.
5-8.
The
3455A
Adjustments must be performed
in
the
sequence
in
which
they
are
presented.
If
the
dc and
ohms
accuracy
of
the instrument
are satisfactory,
the
DC
Zero
Adjustments and Reference Adjustments can be omitted
and
the
RMS
or
Average Converter adjustments can be
performed
to
optimize
the ac
voltmeter accuracy.
5-9.
TEST POINT
AND ADJUSTMENT
LOCATIONS.
S-10.
Test points
and adjustments
arc labeled
on
the top
inner
cover
and
rear
panel (Reference
Module)
of
the
instrument or
arc
shown
in
figures
designated
in
the
adjust-
ment
procedures.
S-11.
DC ZERO ADJUSTMENTS.
Equipment
Required:
DC
Digital
Voltmeter
(-hp-
Model
3490A
or
3455A)
a.
Remove
the
34SSA
top outer cover
and
top
inner
cover
to gain access
to the
AlO
(Mother)
board.
b.
Set the
34SSA
controls
as
follows:
FUNCTION
DCV
Figure
5-1.
100
Volt Zero Adjustment.
RANGE
10
V
HIGH RESOLUTION
ON
AUTO CAL
OFF
GUARD
ON
TRIGGER
INT
MATH
OFF
c.
Set the
test
DVM
to
measure dc
volts
(autorange).
Connect
the
DVM's
low
input to the
A1 0
board ground
test
point
and
the high input to
AlOTOI
(Figure
5-1).
d.
Adjust
A10R66
(Figure 5-1)
for
a
DVM
reading
of
0
V
±
50
microvolt.
Disconnect
the
test
DVM.
e.
Set the
3455A
RANGE
to
lOOVand
AUTOCALto
ON. The
3455A
Reading
should be
0.0000
V
±
1
count.
If
it
is
not, repeat
Steps
b
through
d.
If
this
does not
correct
the
problem,
refer
to
Section
VIII
for
troubleshooting
information.
f.
Reinstall
the
top
inner cover with
two
or
three
screws
and
reinstall
the lop
outer cover
(bottom
covers
must
be
installed).
g.
Set the
3455A RANGF.
to
1
V.
Connect
a
copper
shorting strap across the
3455A INPUT
terminals.
h.
Allow
the
3455A
to
run
at
room
temperature
for
at least
30
minutes.
i.
The
3455A
reading should be
0.000000
V
±
4
counts.
If
it
is,
proceed
to the
DC
Reference
Adjustments
(Para-
graph
5-12).
If
it
is
not.
it
will
be
necessary to
change
the
value
of padding
resistor
AlORIlO
as
outlined
in
the
following
steps.
j.
Record
the
3455
A
reading:
.
5-1
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