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Further
Procedural
Information
4708
Specification
Formats
The
specifications
can be found
in
two
forms:
a.
Tabular
layout as
in
Section
6.
In
Section
6,
the
stability
and
relative
accuracy
specifications
alone describe
the true
performance of
the
instrument
in
a
form which can be
made
traceable
to
National Standards
merely
by
adding
in
the
uncertainty
of
the
reference standard
used
for
checking. Datron's
calibration
uncertainty
is
shown
in
a
separate
column.
This
must be
added,
to
obtain
true
traceable
accuracy
for
all
instruments
which were
last
calibrated
by
Datron.
For
instruments
calibrated
by
other agencies,
their
own
calibration uncertainty
must
be added
instead.
b.
Specifications
stored
within
the
instrument's
non«volatile
memory.
(Refer
to
Section
4 page
4-1
1
to
4-12)
The
instrument's non-volatile
memory
figures
can
be
accessed using
'Spec'
Mode.
These
are
compiled
specifically for
users
without
verification
facilities,
so
that
they
can
obtain
the tolerance limits
of
the
4708
output,
without
referring to
Section
6.
The
position
of
the
CAL
INTERVAL
switch
on
the rear
panel
selects
the
readout
for the intervals
listed
below.
The
'90-day'
and
*l-year'
readouts
always
include Datron's
own
calibration uncertainty,
giving
traceable accuracies
for
instruments
which were
last
calibrated
by
Datron.
24hr
CALIBRATION INTERVAL
24 Hours
Stability figure
only,
relative to
Calibration Standards.
90dy
CALIBRATION INTERVAL
90 Days
Relative
Accuracy
figure
plus Datron's
Calibration Uncertainty.
lyr
CALIBRATION INTERVAL
1
Year
Relative
Accuracy
figure
plus Datron's
Calibration Uncertainty.
Verification
Conditions
The
24-hour
stability
specifications
are
relative
to
user's
reference standards.
In
all
cases
validity
depends on
using
the
same
standard
as reference,
under
the
same
condi-
tions,
including temperature. Also,
verification
is
valid
only
within
24
hours of
calibration
or within
24
hours of a previous
verification.
In the
latter
case, the specifications are relative
to the figures
obtained
at
the
earlier verification.
On
Receipt,
the
90-day and
1-year tolerances
can be
calculated
by adding
both
the
user's
reference standard abso-
lute
uncertainty
and
Datron's
calibration uncertainty
to
the
Relative
Accuracy
figure
(See
the
Report
Sheets).
Following
User
Calibration or a
Previous
Verification,
add
only
the
user's
uncertainty
to the
Relative
Accuracy
figure.
Where
ambient
temperatures
are outside the
Specified range,
temperature
coefficient correction
should
be
taken
into ac-
count.
Appendix 2
describes
the uncertainties inherent
in
any
veri-
fication
process.
Worst-case
figures
must
always be
as-
sumed,
although
acccumulated
uncertainty
is
generally
much
less
than implied.
Report
Sheets
Please use
the printed report sheets as
masters
to
generate
duplicate copies, then record the instrument's
performance on
the duplicates (both
on
receipt
from Datron and
for future
periodic checks).
The
report sheets
list
the appropriate
accuracy
limits (relative
to
Calibration Standards)
and
Datron's
calibration uncer-
tainty
at
the verification points.
Blank columns
are
provided
for the user's calibration uncertainty, the
cumulative
'Valid-
ity'
tolerance
limits,
and
the
DC
Voltage
Standard's adjusted
reading
(for
comparison
with
the tolerance).
Page
1
of
Report Sheet
RS
1
is
assigned
to
guidance
for
those
users
who
are unfamiliar
with
the Verification process.
The
appropriate
limit calculations
appear
in
Appendix
1.
7-A3-4
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