Keithley 2001 Operator's Manual page 272

IEEE-488 Reference
Description
4-114
Short-form formats: :curr:ac:aper?
:curr:ac:aper? xxx
:volt:ac:aper?
:volt:ac:aper? xxx
:res:aper?
:res:aper? xxx
:temp:aper?
:temp:aper? xxx
where; xxx = def, min or max
Response message: 166.6666666667e-6 to 200e-3 seconds
These commands are used to set the integration period for the measurement functions. The in-
tegration period for a triggered reading (measurement) can be expressed as aperture (seconds
per integration). In general, a short integration period provides a fast reading rate, while a long
integration period provides better accuracy. Typically, the selected integration period is based
on a compromise between speed and accuracy. Any triggers received while the instrument is
processing a reading will be ignored.
An alternate way to set the integration period is by basing it on the number of power line cycles
(see :NPLCycles command). If the number of power line cycles per integration (NPLC) is al-
ready known, aperture can be calculated as follows:
Aperture
where; Aperture is the integration rate in seconds per integration.
NPLC is the number of power line cycles per integration.
f is the power line frequency. (Note: For 400Hz line power, use 50Hz to calculate ap-
erture).
Keep in mind that when the integration period is set using the :APERture command, the value
for the :NPLCycle command will change accordingly to reflect the new integration period. Con-
versely, if the integration period is set using the :NPLCycle command, the value for the :APER-
ture command will change accordingly.
On power-up, the instrument will use the NPLC value to determine the integration period. Thus,
if using a different power line frequency, NPLC will remain the same, but aperture may change.
Note: If line synchronization is enabled (see:LSYNc command in SYSTem subsystem), the in-
tegration period will not start until the beginning of the next power line cycle. For example, if
a reading is triggered at the positive peak of a power line cycle, the integration period will not
start until that power line cycle is completed. The integration period starts when the positive-
going sine wave crosses zero volts. See
10OUTPUT 716; ":curr:ac:aper 16.67e-3; aper?"
20ENTER 716; A$
30PRINT A$
40END
:curr[:dc]:aper?
:curr[:dc]:aper? xxx
:volt[:dc]:aper?
:volt[:dc]:aper? xxx
:fres:aper?
:fres:aper? xxx
NPLC
=
-------------- -
f
paragraph 3.12 for more details.
2001-900-01 Rev. K / August 2010