Keithley 237

SECTION3
IEEE-488
Reference
CHU
IV
4.170
v
CHI!'P'~-<1!1="--'"'"'""---'-------------------'
LO
RES?
CHI
RISE •
110.
Oa•
A.
1
J.1A
into
4.17MO
on
1
J,tA
Range
Figure
3-30.
Current
Overshoot
+
CHU
IV
A
1-
-414aV
VERT
4.170
v
CHI
RISE •
2.
82-
B.
1
J,tA
into
4.17MO
on
1
OJ.IA
Range
Table
3-11. Typical
Source
Range
Change
Times
Present
Range
1nA-100nA
1~A-10mA
1nA-100nA
23msec 5msec
1J.lA-10mA
23msec 5msec
100mA
24msec
5msec
1A 36msec 18msec
1.1V,
llV;
1.5V,
15V
-
-
llOV,
llOOV
- -
Minimizing
Measurement
Time
The selections for
AID
hardware
integration times
dur-
ing each measure
phase
are listed
in
Table 3-12. The
measure times are
with
the filter disabled
and
a fixed
measure range. Your
throughput
can
be
optimized
by
knowing which integration time
and
measure range to
use. For maximum throughput,
use
only as
much
resolu-
tion as
you
need.
As
an
example, consider a measurement requiring 1
pA
sensitivity, which can
be
made
on
the 1nA
or
10nA
range.
Assuming the external system noise
is
low,
you
could use
416~sec
integration time (4-digit resolution). From
Figure3-27, the 1nA range settles to
0.1%
(1pA)
in
ap-
proximately
7.7't.
The
't
from Table
3-10
is 60msec, so
that
yields 462msec.
Adding
the 1msec measurement time
from Table 3-12 gives a total of 463msec,
or
about 2.2
readings
per
second.
3-86
Next Range
1.1V, 11V;
+
lOOmA
lA
1.5V,15V 110V,1100V
3msec 10msec
-
-
3msec 10msec
-
-
-
10msec
-
-
14msec
-
-
-
- -
5msec 10msec
-
-
10msec 5msec
Table
3-12.
Measure
Times
Integration
Measure
Time
Resolution
Time
416~sec
4-digit
1msec
4.0msec
5-digit
5msec
16.67msec
5-digit
23msec
20.0msec
5-digit
27msec
On
the 10nA
range,
with
a 4msec integration time (5-digit
resolution), the range settles to
0.01%
(1pA)
in
about
10.1't.
For the
10nA
range,
that
is about 131msec (from
Table
3-10).
Adding
the 6msec measurement time (from
Table 3-12) gives 137msec,
or
approximately
7.3
readings
per
second.