Keithley 237 - Page 104

SECTION2
Operation
2.16
FILTER
J
TIME SUPPRESS
De De
ALTER
AUTORANGE
••De
MEASURE
Filtering is
used
to stabilize noisy measurements. The
unit
does this
by
averaging a
number
of
reading conver-
sions
and
then
displaying (or storing)
the
result. The
number
of
readings
that
can
be
averaged (filtered) is 2, 4,
8, 16
or
32. FILTER disabled is synonymous to averaging
one reading.
The more filtering used,
the
quieter
the
reading.
How-
ever, filtering increases measurement time,
thus
decreas-
ing
unit
speed. As a general rule, only
use
as
much
filter-
ing
as necessary.
The FILTER light denotes
the
status
of
the
filter.
If
the
light is on, the FILTER is enabled.
If
the
light is off, FIL-
TER is disabled. The FILTER
button
toggles between
the
filter selections
and
normal operation.
Perform the following steps to control the filter from the
front panel:
1.
Press FILTER.
If
its light
was
off (FILTER disabled),
it
will
turn
on. The present filter selection will
be
dis-
played. For example,
if
the
FILTER is currently dis-
abled the following is displayed:
DISABLE
FILTER
2.
If
no
changes are to be made, press FILTER
or
EN-
TER to
return
to
the
source-measure display state.
Otherwise,
use
the
SELECT
buttons
to display
the
desired filter selection (see Figure 2-30).
+
3. Press ENTER.
NOTES
1.
A
unique
filter value can
be
set
for each source.
2.
The
unit
will
power
up
to the last
programmed
filter
for the selected source.
3. Factory initialization will disable FILTER for
both
sources.
4. For pulse sweeps,
the
increased measurement time
caused
by
filtering causes delay times to
be
recalcu-
lated
by
the
Source
Measure Unit
in
order
to main-
tain the
programmed
ON
and
OFF times.
5.
Total measurement time for each reading is depend-
ent
on
the
number
of
conversions averaged (filter)
and
the integration rate currently selected (see para-
graph
2.15).
IEEE-488 Bus
Operation
The P
command
is
used
to control
the
filter.
PO
=
Filter disabled
P1
=
Two readings averaged
P2
=
Four
readings averaged
P3
=
Eight readings averaged
P4
=
16 readings averaged
P5
=
32 readings averaged
HP
BASIC 4.0
Programming
Example:
OUTPUT
716;
"P3X"
OUTPUT
716;
"POX"
FILTER enabled; eight
readings averaged.
FILTER disabled.
Complete information
on
the
IEEE-488
bus
and
this com-
mand
can
be
found
in
Section 3 IEEE-488 Reference.
I
DISABLE
FILTER
I
12
RDG
FILTER
I
14
RDG
FILTER
I I
8
RDG
FILTER
I
116
RDG
FILTER
I
132
RDG
FILTER
I
~SELECT
C>
Figure
2-30.
FILTER
Selections
2-52
+