Datron 4708 User Handbook Manual page 99

AC
Current
Verification
(100|J.A-1A
Full
Range
Values)
Summary
of Verification
Procedures
Full
Range
Current
(Using
Standard Shunts)
The
Thermal Transfer Current
Shunt
is
fitted to
the
Shunt
Input of the
Thermal
Transfer Standard
and
the
4708
set to
output a
Full
Range
current into the shunt
at
the required
frequency
(or
Spot Frequency).
The
output current
is split
between
the
shunt
and
the transfer
element. This
is
compared
with
the
output
from a Standard
DC
Current Source.
See Page 7-26
for the
procedure.
Alternative
Method
The 4708
is
connected
up and
set to
output a Full
Range
current into the calibrated
AC
Current Shunt
at
the
required
frequency (or
Spot Frequency).
The 4708
Current output
develops a
voltage across the shunt which
is
measured by
the
AC DMM,
with care taken not
to
load the shunt.
The
procedure
is
detailed in
Appendix
5.
Interconnections
Interconnection
instructions in this
section are necessarily
simple
and
basic,
and
are
mainly
intended
to
show
connec-
tions
to
the
4708.
It is
recognized
that
they
may
need
to
be
adapted
to
meet an
individual user's
requirements.
It is
assumed
that
users will possess
knowledge
of the operation
and
use of standards
equipment such
as that
mentioned above.
Equipment Requirements
A
DC
Current Source of
suitable
accuracy
and an
AC/DC
Thermal Transfer together with a
set
of
Calibrated
Thermal
Transfer Current Shunts of
suitable
accuracy.
For
the alternative
method
at
Appendix
5,
a
set
of
calibrated
AC
Current Shunts of
suitable
value
and
accuracy.
Preparation
Before
attempting
any
verification
ensure
that
the follow-
ing steps
have been
carried out.
1
.
Turn on
the
instrument
to
be checked and allow
at least
2 hours
warm-up
in
the specified
environment.
2.
Cancel any
MODE
keys,
ensure
OUTPUT
is
OIT
and
check
that
'cal' is
not present
on
the
MODE
display. (If
'cal' is
present, turn the Calibration
Keyswitch on
the
Rear
Panel
to
its
RUN
position).
3
.
Before connecting
and
operating
any equipment,
consult the
manufacturers'
handbooks.
4. Self-Test:
Press the Test'
key
to
carry out the
test
routine
described
in
Section
4.
Terminate
the
test
routine.
5. If 'Spec'
Mode
is
required, select either
24hr,
90dy
or
lyr
on
the
Rear
Panel
CALIBRATION INTERVAL
Switch.
When
received
from
Datron,
90dy
is
the
relevant selection.
The
report sheets
hold
figures for
this interval.
7-24