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INSTRUCTION MANUAL
MAINTENANCE
Digital
Mullimeter
Models 172A.
113A
0 I
e.
Adjust
potentiometqr
R714 (input
current)
to obtain
the
same reading
as
in
step
c.
reading.)
(Minimize
physical
movement
around
input
as this
will
cause
a shift
in the
f.
Repeat
steps
b.
thru
e.
acceptable.
t0
assure
equal
readings
(within
+ I digit
is
NOTE
Each digit
difference
between
input
shorted
and 2Mfll/IuF
applied
is 5 picoamperes
dc
2)
Ohms Zero
Adjustment.
a.
Set
the
OMM to Z-WIRE and LO ohms.
b.
Select
3KR range.
0"'
Apply
short
between
input
HI and LO.
2 d.
Adjust
potentiometer
R713 (ohms zero)
for's
zero
or
zero
flashing
one
reading
on the
DMM.
e.
Select
30K0
range.
f.
Slightly
readjust
R713 to obtain
a zero
or
zero
flashing
one
reading.
b.
DC Voltaqe
Calibration.
I)
Zero
Adjustments.
a.
Select
DCV 300mV range.
b.
Connect
the
DC Calibrator
(A)
to
the
input
terminals.
NOTE
It
may be necessary
to compensate
for
dc offset
of
the
DC Calibrator.
For example,
if
the
dc offset
is
-2 uV dc then
the
DC Calibrator
should
be adjusted
+2 uV to
compensate
for
the
offset.
Use a Keithley
Model
I55
to determine
calibrator
offset
($1
Set
the
DC Calibrator
to apply
+lOOpV,
+luV
to OMM input.
Adjust
potentiometer
R204 (300mV zero)
for
a 00.10
reading
on
OHtl.
e.
Select
30Vdc
range.
@Ii
Set
the
DC Calibrator
to apply
+IOmV +_lOOuV to DMM input.
Adjust
potentiometer
~207
(30V zero)
for
a 0.010
reading
on DHH.
2)
Full
range
Adjustments.
a.
Connect
the
DC Calibrator
to
the
input
terminals.
b.
Set
the
instrument
to the
range
given
in Table
6-T.
C.
Set
the
DC Calibrator
to provide
the
"Applied
Input"
given
in Table
6-10.
d.
Adjust
the
control
given
in Table
6-10
to achieve
the
specified
display.
NOTE
Perform
the
calibration
in
the
exact
order
given.
6-
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