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Verify
each range
in
the
sequence
of
RSI
Table
1
(a)
as follows:
a.
Appendix
3
Read
the
notes
on
the
use of
the
Null
Detector.
b
.
Both
voltage sources
Set output
to
zero.
c
.
Null Detector
Set
to
low
sensitivity.
d
.
With
both outputs
OFF,
connect
the
DC
Voltage
Standard
and
the
4708
to the
Null Detector
as
shown
in
the
diagram
for
High
Voltage,
and
allow
the
circuit to stabilize
thermally.
Ensure
correct
Guard and
Sense
selections.
e
.
DC
Voltage Standard
Set
to
the correct polarity
and
voltage
(see
RS
1).
f
.
4708
(see
RSI)
i
.
Ensure
that
DC
and
the
correct
OUTPUT
Range
are
selected.
ii.
With
OUTPUT
OFF,
use
the
OUTPUT
H
keys
to set
the correct polarity
and
voltage
on
the
OUTPUT
display.
CAUTION:
In operation
(iii),
pressing
the
wrong
ON
key
will result in
approximately twice
the
output voltage
being connected
across the
Null
Detector.
iii.
Press
the correct-polarity
OUTPUT
ON
key.
g
.
DC
Voltage Standard
Set
OUTPUT
ON.
h. Null Detector
Increase
sensitivity to
give an
off-null
reading.
j
.
DC
Voltage Standard
Adjust output
voltage
to
give a
null
on
the
Null
Detector.
k
.
Repeat
(h)
and
(j)
until
the null
lies
between two
consecutive values of
DC
Voltage Standard
Output,
at
the
same
resolution as the
4708
OUTPUT
display.
l
.
DC
Voltage Standard
Record
output voltage
on RSI.
m.
Repeat
(e)
to
(1)
for
all
4708
outputs
on
RSI
Table
1(a).
n.
DC
Voltage Standard
Set
OUTPUT
OFF.
p.
4708
Set
OUTPUT
OFF.
q
.
Sum
the Verification setup uncertainties
and
record
in
the
Us
column
as voltage deviations.
(Refer
to
Appendix
2).
Validity
Tolerance Limit
Calculations
Refer
to
Appendix
1
page
7-A
1-1,
para
1.
r.
Calculate
the
two
Validity
Tolerance
Limits:
Use
Calculation
A
if
the
4708 was
last
calibrated
by
Datron.
Use
Calculation
B
if
the
4708
was
last
calibrated
against the standards
being used
for verification.
Each 4708
Full
Range
output
is
verified
if
the
DC
Voltage
outputs
recorded
in
(1)
are
at
or
between
the
corresponding
Validity
Tolerance
Limits.
Linearity
(10V
Range)
s
.
If
the
lOV Range
verified correctly,
repeat operations
(e)
to
(r)forRSl
Table
1(b).
If
the
Low
Voltage
Ranges
verified,
proceed
to
High
Voltage
Ranges
verification.
7-4
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