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AC
Current
Verification
Procedure
(Using
Thermal
Transfer,
Current Shunts
and
DC
Current Standard)
Record
results
on Report
Sheet
4708
RS
1,
Table
5 (Page
7-35).
Full
Range Checks (1mA
-
1A)
THERMAL TRANSFER
STANDARD
INPUT
TRANSFER
UNIT
1
o<!=^
OUTPUT
a
.
With 4708
OUTPUT
OFF,
set
the
Function
to
I,
OUTPUT RANGE
to
10mA,
OUTPUT
Display
to
10.(XX)00mA
at
a Frequency of 300Hz.
b
.
Configure
the
Thermal
Transfer
for
10mA
Current
measurement and
connect
the appropriate
shunt
between
Transfer
Unit
and Thermal
Transfer Standard.
c
.
With
OUTPUT
OFF,
connect
the
4708
1+
and
I-
to
the
Transfer
Unit
AC
inpuL
d
.
Set
the Transfer
switch
to
'AC.
Set
4708
OUTPUT
ON,
and
null the
Thermal
Transfer
to
the
4708
AC
OUTPUT.
Set
4708
OUTPUT
OFF.
e
.
With
OUTPUT
OFF,
configure the
DC
Current
Standard
for
10mA
output,
and
connect
to the
Transfer
Unit
DC
inpuL
Set
the
Transfer switch
to
'DC.
f
.
Set
the
DC
Standard
OUTPUT
ON
and
adjust
its
output
current
to null the
Thermal
Transfer. Set
its
OUTPUT
OFF.
Record
its
output current
on
RSI
Table
5(a).
g
.
Set
4708
Frequency
to
5kHz, and
repeat
(c)
to
(f).
h. Repeat
(a) to (g),
but
for
4708
100mA
and
lA
Full
Range
outputs.
j
.
If
the
Thermal
Transfer has
been
adequately
calibrated
for
1mA
transfers,
repeat
(a) to (g) for
4708
1mA
Full
Range
outputs,
recording
the
DC
Standard output
currents
in
RSI
table 5(b).
k
.
Sum
the Verification setup uncertainties
and
record
in
the
Us
column
as current deviations.
(Refer
to
Appendix
2).
Validity
Tolerance Limit
Calculations
Refer
to
Appendix
1
page 7-Al-l
Para
1
l
.
Calculate
the
Lower
and Upper
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.
m
.
Each
Full
Range
output
verifies
if
the
DC
Current
outputs recorded
in
(f)
are
at
or
between
the
corresponding
Validity
Tolerance
Limits.
7-25
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