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j)
Null Detector
Set
to
LOW
sensitivity.
c)
Re-standardizing using
"STD"
To
re-standardize
all
DC
Voltage
and
Current
ranges
in
the
same
ratio,
carry
out
steps
1,
2, 3,
then
either
6 and
7,
or 8
and
9.
In
operation
(g)
of
the Calibration
Routine,
substitute
"STD"
for
"SET".
(Refer
to earlier
description
of
"STD").
3.
Calibration Routine:
Calibration
of
DC
Voltage
to
a Standard voltage
calibration
source.
k)
4708
Press
Not
applicable
if
operation
(g)
omitted
CAL
key:
CAL LED
flashes once.
MODE
display
is
trans-
ferred
to
OUTPUT
dis-
play.
MODE
display
is
cleared.
SET
LED
goes
OFF.
The 4708
is
now
calibrated
at
this
value.
NOTES:
A
For
calibration
at
any
value,
this
routine
may
be
used
as printed.
B
For
calibration
at
zero or positive
nominal
Full
Range
only, operation
(g)
may
be
omitted.
C
In
Table
8.2(a),
use interconnections
as
Fig. 8.1(a)
(Low
Voltage), obtaining the
correct calibration voltage
from
the
source.
In
Table
8.2(b),
use
interconnections as
Fig. 8.1(b)
(High
Voltage)
selecting
+
10
atsteps
lOand
1
1,+ lOOatsteps
12and
13.
CAUTION:
Below
2%
of
Range,
the
4708
corrects for
an
assumed
offset
error, at
2%
of
Range
and above
the correction
is
for
an
assumed
gain
error.
a)
Null Detector
b)
4708
c)
DC
Source
d)
4708
e)
4708
Set
to
Low
sensitivity.
Ensure
OUTPUT
OFF.
Set
to
the required polarity
and
value.
Select correct
FUNCTION
and
RANGE.
Use
Full
Range, Zero
or
OUT-
PUT
1 4
keys
to set the
required
polarity
and
value
on
OUTPUT
display.
N.B.
Operation
(0 must be
carried
out before operation
(g).
f)
4708
Press
the correct-polarity
ON
key.
±0 Alignment
Routing:
Alignment
of
lOV Range
positive
and
negative zeros
if
neces-
sary
at
step 3
of Table
8.2.
a)
Null Detector
Set
to
low
sensitivity.
b)
4708
Ensure
OUTPUT OFF
on
DC
lOV
Range.
c)
Calibration
Source Ensure
set to
zero and
thermally
stable.
d)
4708
Press
OUTPUT
Zero
Key.
Press
ON+
Key.
Press
±0
Key:
±0
LED
lights,
OUTPUT
display
at zero.
e)
Null Detector
Increase
sensitivity to
give an
off-
null
reading
and
use
4708
OUT-
PUT
1
4^
keys
to
back
off
to
null.
Repeat
until
null
lies
between two
values
of
the
OUTPUT
display
least-significant
digit.
0
4708
Press
CAL
key:
CAL LED
lights.
No
change
to
OUTPUT
display.
g)
4708
Press
ON-
key.
h)
Null Detector
Obtain
accurate
null
as
in
(e)
above.
j)
4708
Press
CAL
key:
CAL LED
goes
OFF.
±0
LED
goes
OFF.
OUTPUT
display
falls
to
zero.
The4708
positive
and
negative zeros
are
now
both aligned
to
the
Calibration
Source
zero.
Omit
Operation
(g)
if
calibrating
at
zero
or Full
Range
value.
g)
4708
Press
SET
key:
SET
LED
lights
green.
OUTPUT
display
reading
also
appears
on
MODE
display.
h)
Null Detector
Increase
sensitivity to
give
an
off-
null
reading
and
use
4708
OUT-
PUT
1 4 keys
to
back
off
to
null.
Repeat
until null
lies
between two
values
of
the
OUTPUT
display
least-significant
digit.
8-5
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