Special Operations - Fluke 8506A Instruction Manual

8506A
from
the
measured
value to display
only
the deviation.
Scaling
and
Offset
can be used
in
combination
to display
percentage
variation.
Examples
of
such operations
are
given
in
Applications later in this section.
2-104.
Use
of
mathematic operations
is
expressed
in
the
following formula:
DISPLAY
=
MEASURED VALUE
SCALING
(OR
EXTERNAL
REFERENCE)
-
OFFSET
Measured
value
in this
formula
refers
to the
measurement
as
influenced
by
all
selected
measurement
parameters.
This value
is
subject to the
following function-dependent
considerations.
1.
VDC
or
OHMS
functions:
any
applied zero
value
is
first
subtracted, yielding the
measured
value.
2.
VAC
functions:
External Reference cannot be
used.
2-105.
SCALING
NOTE
If the
multimeter
is
in
both
Scaling
and
Offset
modes,
the scaling
value
is
applied before the
offset value.
2-106.
The
Scaling
mode
divides the
measured
value
(after
application of
V
DC
or
OHMS
zero) by a
known
amount
and
displays the quotient. Ratios, percentage
deviations,
or input/ output
relationships
can thereby be
displayed.
The
scaling divisor
may
be a previously
displayed
and
stored value, or
any non-zero numeric
entry
from
+10
9
to
-HO" 9 and from
-lO
9
to
-10 9
.
When
compared
to
External Reference, Scaling
offers a
much
wider
range.
Only one
scaling factor
may
be stored
at
a
time.
2-107.
Storing
the
displayed value
as a scaling factor
warrants
a
word
of caution: ensure
that the
displayed
value
is
the true original display by
first
toggling out of
Scaling
and
Offset
modes
(respective
annunciators
off).
No
stored scaling or
offset
value
is
lost in this
manner.
To
store the desired display,
push
STORE
SCALING.
2-108.
EXTERNAL REFERENCE
NOTE
External Reference
mode
is
not available
in
ac
voltage functions
(NORM
AL,
ENH'D,
or
HI
ACCUR).
Attempting
to
enter
External
Reference
mode
in
any
VAC
function causes
an Error
A
condition.
2-1
10.
Immediately
after a
power-up
or
reset,
RECALL
EXT REF
can be used
to verify the multimeter's software
number.
The
first
subsequent
use of
EXT REF
to activate
External Reference
mode
disables
this
software
identification feature.
When
enabling External Reference
mode,
the reference voltage
is
displayed
as
long
as the
EXT REF
button
is
depressed.
The
EXT
annunciator
is
lighted
when
the
mode
is
enabled.
2-1
II.
The
external reference voltage
may
be
a
maximum
of
±2QV
dc
on
either
high or low
External
Reference input with respect
to
VOLTS INPUT
LO. The
voltage
between External Reference
high
and low
may
not exceed
40V
dc.
The minimum
acceptable External
Reference
voltage
is
the greater of
±100 uV
or a value
found
with the following formula:
±
Vin
Vmin
=
10
9
2-1
12.
Usually, the
External Reference low
terminal
is
externally
tied
to
VOLTS INPUT
LO.
In
any
event, the
resistance
between
either
External Reference terminal
and
VOLTS INPUT LO
should be
less
than 20 kilohms.
A
reading
rate
of
eight
samples-per-reading and
filter
bypass
are specified for the
External Reference
input.
2-113.
OFFSET
2-114. In Offset
mode,
the display represents the
deviation
from
a stored
offset
value.
Measurements
of
stability
or
analog
variation are thereby
possible.
The
multimeter automatically
subtracts a
programmed
numeric
(or previously stored display value)
from
the
measurement and
displays the
result.
No
increase
in
resolution
is
displayed while
in
the Offset
mode.
One
value (whether a
numeric
or
a
previous
display)
may
be
stored
at
a time.
Programmed
numerics
may
range
from
+10 9
to
-10 9
.
The
stored offset
value
may
be
recalled at
any
time.
2H15.
Special
Operations
2-116.
PEAK
2-117.
The
highest
and
lowest deviations
in the
displayed value
may
be
recorded
in
the
Peak mode.
Source
stability
may
thereby be
checked over
a period of
time.
The
PEAK
push
button toggles
into/'
out of the
Peak mode. High and low Peak
values
may
be recalled
at
any time without exiting the
Peak
mode
or interrupting
further
peak
recording.
The
following sequence
is
used:
RECALL
HI
PEAK
RECALL LO PEAK
2-109.
Scaling
and
External Reference
modes
are
mutually
exclusive: selection of either
mode
automatically disables the other.
The
External Reference
value (always
measured
as
a dc
voltage)
is
applied as
an
unswitched
input
through
the rear input connector.
The
high or
low peak value
is
latched
in
the display as
long
as the
PEAK
button
is
held depressed,
2-118. Exiting the
Peak
mode
(toggle
PEAK
once)
halts
further
peak recording, but does not erase previously
2-27