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Model
3455A
Section
IV
b.
If
the
DVM
reading
is
out of
tolerance
by
a per-
centage
that
is
greater
than
the
maximum
allowable
error
of
the standard, the
DVM
is
dermitcly outside
of
its
specifica-
tion.
c.
If
the
DVM
reading
is
in
or
out
of
tolerance
by
a per-
centage
that
is
less
than the
maximum
allowable
error
of
the
standard,
it
is
in
one of
the
ambiguous
regions
(shaded
areas)
shown
in
Figure
4-1.
The
DVM
may
or
may
not
be
within
its
specification
and
the
only
way
to
tell
for
sure
is
to
use
a
more
accurate standard.
4-24.
As
the
accuracy
specifications
of
the
standard
approach
the specifications
of
the
DVM
to
be
tested,
the
ambiguous
regions sliown
in
Figure
4-1
become
wider and
the
uncertainty
contributions
of
the
standard
become
increasingly
significant.
If
the standard
is
less
than
three or
four times
more
accurate than the
DVM.
the
performance
test
is
not
practical
because
the
ambiguous
regions
cover
most of
the
DVM's
error range.
From
a
practical
stand-
point, the
dc standard should be
at least five
times
more
accurate
than
the
34S5
A
specifications
to
be
tested. If
such
a
standard
is
nut
available,
an
alternative
approach
is
to
use
a
calibrated
standard
that
is
extremely
stable
and
(pre-
ferably)
two
to
four times
more
accurate than the
3455A.
When
this
is
done,
the
correction
factors
given
on
the
dc
standard's calibration chart
must
be
algebraically
added
to
the
34SSA
test
readings.
Test
validity
depends on
the
calibration
uncertainties
and
the short-term
stability
of
the standard.
4-25.
The
Reference Divider
recommended
in
the follow-
ing
DC
Voltmeter Accuracy
Test
is,
according
to
its
pub-
lished specifications,
accurate
enough
to
test
all
but
the
1-
volt
and
10- volt full-scale
24-hour
specifications.
The
1-
volt
and
10- volt full-scale
specifications
can be
tested
using
the
DC
Transfer
Standard
also
recommended
in
the pro-
cedure.
4-26.
OPERATIONAL
VERIFICATION TESTS.
4-27.
DC OPERATIONAL ACCURACY
TEST.
4-28.
The
DC
Transfer
Standard
required
for
the
following
test
must
be
calibrated to a 1.017
V
to
1.019
V
standard
cel)
that
has been
calibrated
by
the
National
Bureau of
Standards (NBS).
If
the
345SA
is
to
be
tested
for
its
24-hour accuracy
specifications,
the
Transfer
Standard must be
adjusted
for
optimum
1-volt
and
10-volt
output accuracy
using
NBS-calibrated
stan-
dards.
It is
recommended
that
the
Transfer Standard be
calibrated
and
adjusted
just
prior to
use.
After
calibra-
tion,
it
should be
left
on
and,
if
possible,
kept
in
a
con-
trolled
environment where
the
ambient temperature
is
within
one
or
two
degrees
of
the
temperature
in
which
it
was
calibrated.
The
following
procedure should be
per-
formed
in
that
same
environment.
4-29. If
the
recommended
DC
Transfer
Standard
or
its
equivalent
is
not
available,
an
NBS-calibrated standard
cell
(1.017
V
to 1.019
V) can be
substituted.
If this
is
done, check
the
full-scale
accuracy of
the
345SA
1
V
and
10
V
ranges using the Reference Divider
recommended
in
the procedure.
4-30.
Tatt Procwlura.
Equipment
Required:
Reference
Divider (Fluke
Model
7S0A)
DC
Transfer
Standard
(Fluke
Model
731A)
DC
Standard
(Systron
Donner Model
M106A)
DC
Null Voltmeter
(-hp-
Model 419A)
a.
Set
the
34SSA
controls as follows:
FUNCTION
DCV
RANGE
1
V
HIGH RESOLUTION
ON
AUTO CAL
ON
GUARD
ON
TRIGGER
INTERNAL
b.
Set the
DC
Transfer Standard
for
an
output
of
1
V.
Connect
the
output of
the transfer
standard
to
the
3455A
INPUT.
c.
The 34S3A
reading should
be
within the
test
limits
listed
in
Table
4-1
,
verifying
its
1-volt full-scale
accuracy
with
High
Resolution on.
d.
Set the
3455A
RANGE
to
10
V.
The 3455A
reading
should be
within the
test
limits listed in
Table
4-3,
verifying
its
10-volt tenth scale
accuracy
with
High
Resolution on.
e.
Set the
Transfer Standard
for
an
output of
10
V.
The 345SA
reading should be within the
test
limits
listed
in
Table
4-1 verifying
its
10-volt
full
scale
accuracy with
High
Resolution on.
Table
4-1.
DC
Accuracy
Tast
(1
V.
10
V
Full
Scala;
High
Ratolutioa
On).
Lflvei
Range
24
Houi
Te$( Llmiit
90
Day
Test Limits
1
V
10
V
1
V
10
V
0 999966
to
1
.000034
9.99977
to
10.00023
0.999936
to
1.000064
9.99947
to
10.00063
f.
Set the
3455A
HIGH RESOLUTION
to
OFF. The
34SSA
reading
should be
within the
test
limits
listed in
4-3
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