Datron 4708 User Handbook Manual page 101

Resistance
Verification
(lOQ-lOOMD
Fixed Values)
Summary
of Verification
Procedures
a,
4-Wire Values
The 4708
is
set to
'Remote
Sense'.
Its
four output
terminals
are
connected
to
a suitable
DMM,
configured
in
'4-wire Resistance'
mode.
Each
standard
resistor
is
thus
measured
at
its
internal
4-
wire
terminals,
and
the
DMM
reading
is
recorded.
The
calibrated
value present
on
the
OUTPUT
Display
is
also
recorded; the specification tolerances
and accumulated calibration uncertainties are added.
The measured
value
is
checked
against
this result.
The
procedure
is
detailed
on page
7-28.
b.
2-Wire Values
Remote
Sense
is
deselected.
The 4708 Hi and
Lo
terminals are
connected
to a suitable
DMM,
again
configured
in
4-wire resistance
mode. Each
standard resistor
is
thus
measured
at
the 2-wire
terminals
of
the
4708, and
the
reading
is
recorded.
The
difference
between
the
2-wire
and 4-wire
measured
values
is
also recorded;
and checked
against the specification tolerances.
The
2-wire
zero values (including internal
wiring) are
similarly
checked
against specification tolerances.
The
procedure
is
detailed
on page
7-29.
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
ihatmentioned above.
Equipment Requirements
•
A
DMM
of
sufficient
accuracy,
used
to
measure
resistance.
Example:
A
Datron 1281
or 1081.
Alternatively:
•
A
ratiometric
resistance-measuring device of
suitable
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
OFF
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
1
yr
on
the
Rear
Panel
CALIBRATION INTERVAL
Switch.
When
received
from
Datron,
90dy
is
the
relevant
selection.
The
report sheets hold figures
for this interval.
7-26