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MODE/FREQUENCY
4
Keys
The
terminal value
is
changed, without
altering
the
OUTPUT
display,
by
pressing
the
1 4
keys beneath
the
MODE/FRE-
QUENCY
display.
The
gain
compensation
being
applied
is
displayed as
a percentage
or
ppm
of
the
OUTPUT
display
value;
with
positive polarity
for
an
increase of terminal value,
and
negative
for
a
decrease.
The
gain-compensation
factor
has a
maximum
possible resolu-
tion
of
±
O.lppm
of
Full
Range (DCV).
Example
of
the
use
of "Error"
mode
To
measure
the
linearity
of a
DMM,
a user needs
to:
Remove
any
zero
offset.
Detect
and measure any
inherent gain
error
ratio
(usually
from
its
response
to
a
full
range
input).
Calculate
compensating
deviations
for
each of
the
inputs for the
linearity
measurement, based on
the
measured
ratio,
and
Compensate
each
input to
the
DMM
so
that
the
linearity
errors
may
be measured.
In
"Error"
mode, once
the gain error
has
been measured,
the
4708
automatically
calculates
and
applies the
compensating
deviation
to
all its
outputs
on
that
range
and
function, whilst
displaying
both
the
nominal (uncompensated)
value of
output
and
the
compensation
ratio.
Only
if
the
DMM
response
is
linear,
will
each
DMM
reading agree with
the
corresponding
4708
OUTPUT
display value.
In the
following
sequence a
DMM
is
checked
for linearity
.
For
purposes of
explanation,
it
is
assumed
that linearity
is
correct,
but
the
DMM
has a gain
error
of +100.0
ppm.
4708
4708
S«t4708
Output
to
the
(D
selected value
(in
this
case
10V FR)
Observe
that
DMM
reading
is
in
error
4708
Use
MODE
e *
keys
to
oorreci
the
DMM
error
Mode
displays presents
compe
nation
ratio
(
-tOOppm
set
4
(
compensation
value
ratio
set
)
value
4-13
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