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Section
V
Model
3455A
k.
Remove
the
top
covers
and note
the
value
of
A10R106 —
if
there
is
an
R1
10
installed (sec
Figure
5-2).
Refer to Table
5-1
and
record the Offset Voltage
that cor-
responds to
the current value
of
AlORl
10:
(If
there
is
no
AlORl
10,
record
0.000000
V.)
If
R1
10
is
connected
to the terminal
marked
"+".
the polarity
of
the Offset
Voltage
is
negative:
if
RllO
is
connected
to the terminal
marked
the polarity
of
the
offset
is
positive.
l.
Add
the voltages recorded
in
Steps
j
and k
to
obtain
the
total offset:
m.
Refer
to
Table
5-1
and
locate the Offset
Voltage
that
is
closest to
the
total
offset voltage
recorded
in
Step
I.
Obtain
a
resistor that
corresponds
to that offset voltage.
n.
Remove
the
original
AlORl
10
(Figure
5-2).
If
the
total
offset
(Step
I)
is
positive,
connect
the
new RllO
between
the
unmarked
terminal
and
the terminal
marked
if
the
total offset
is
negative,
connect
it
between
the
unmarked
terminal
and
the
terminal
marked
"+".
o.
Reinstall
the top covers
and
again allow the
instru-
ment
to
run
at
room
temperature
for
30
minutes.
At
the
end
of
that
period,
the
34SSA
reading
should
be
0.000000
V
±
4
counts.
If
it
is
not. repeat Steps
j
through
n.
Table
5-1.
DC
Zero Adjustment Padding
List
(A10R110).
Offset
Voltage
Resistor
Value*
-hp- Part
No.
0.6
mV
3M
0683-3055
1.0
mV
1.5
M
0683-1555
1.6
mV
1.0
M
0683-1055
2.0
mV
750
K
0683-7545
2.5
mV
620
K
0683-6245
3.0
mV
510
K
0683-5145
3.5
mV
430
K
0683-4345
4.0
mV
360
K
0683-3645
4.6
mV
330K
0683-3345
5.0
mV
300
K
0683-3045
*AII resistors
are
t
5%,
1/4
W.
Carbon.
5-12.
DC
AND OHMS REFERENCE
ADJUSTMENTS.
S-i3.
The
IX
Transfer
Standard
required
for the
following
adjustments
must
be
adjusted
for
optimum
I-volt
and
10-volt
output
accuracy
using
NBS-calibrated
voltage
standards.
The
Transfer
Standard should be
adjusted
just
prior to
use.
After adjustment,
it
should be
left
on
and,
if
possible,
kept
in
a
controlled
environment where
the
ambient temperature
is
within
one
or
two
degrees
of
the
temperature
at
which
it
was
adjusted.
The
following pro-
cedure should be
performed
in
that
same
environment.
S-14.
Adjustment
Procedure.
Equipment
Required:
DC
Transfer
Standard
(Ruke
Model
731
A)
Standard
Resistor
(1
kilohm
±
0.0005%;
Guildline
9330/1 K)
Standard
Resistor
(100 kilohm
1
0.002%:
Guildlinc
9330/100 K)
NOTE
Ail
of
the reference adjustments are screw-
driver
adjustments
and
are
accessible
through
holes
in
the rear
panel
of
the
Reference
Module
(rear
panel
of
instrument).
Adjustment
Designators
are
marked on
the
panel
The
adjustments should
be performed
after
a 30-
minute
warmup
period with
all
covers
installed.
a.
Set the
3455A
controls
as
follows:
FUNCTION
DCV
RANGE
10
V
HIGH
RESOLUTION
ON
AUTO CAL
ON
GUARD
ON
TRIGGER
INT
MATH
OFF
b.
Set the
DC
Transfer
Standard
for
an output
of
10
V.
Using
short pieces
of
number 20
AWG
(or
larger)
insulated
solid
copper
wire,
connect
the
output of
the Transfer Stan-
dard
to the
3455A
INPUT.
c.
Adjust
the
10
V
pot
for
a
3455A
reading
of
t
10.00000
V.
d.
Set the Transfer
Standard
for
an
output of
1
V.
Set
the
34S5A
RANGE
to
I
V.
e.
Adjust
the
10:1
pot
for
a
345SA
reading
of
1.000000
V(±
1
count).
f.
Set the
3455A RANGF.
to
10
V
and
set
the Transfer
Standard
for
an
output of 10 V.
g.
Repeat
Steps
c
through
f until
optimum
adjustment
is
obtained.
5-2
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