Keithley 2601 Reference Manual page 317

Series 2600 System SourceMeter® Instruments Reference Manual
Remarks • The Series 2600 uses a ratio metric A/D conversion technique. To ensure
accuracy of readings, the instrument must periodically obtain fresh
measurements of its internal ground and voltage reference. The time interval
between needing to update these reference measurements is determined by
the integration aperture being used for measurements. Separate reference and
zero measurements are used for each aperture.
• By default, the instrument automatically checks these reference measurements
whenever a signal measurement is made. If the reference measurements have
expired when a signal measurement is made, the instrument will automatically
take two more A/D conversions, one for the reference and one for the zero,
before returning the result. Thus, occasionally, a measurement takes longer
than normal.
This extra time can cause problems in sweeps and other test sequences in
which measurement timing is critical. To avoid the extra time for the reference
measurements in these situations, the
be used to disable the automatic reference measurements. Keep in mind that
with automatic reference measurements disabled, the instrument may gradually
drift out of specification.
To minimize the drift, a reference and zero measurement should be made just
prior to the critical test sequence.
used to force a refresh of the reference and zero measurements used for the
current aperture setting.
• Autozero reference measurements for the last 5 used NPLC settings are stored
in a reference cache. If an NPLC setting is selected and an entry for it is not in
the cache, the oldest (least recently used) entry will be discarded to make room
for the new entry.
Perform autozero once for SMU A:
Example
smua.measure.autozero = smua.AUTOZERO_ONCE
smuX.measure.calibrateY
Function Generates and activates new measurement calibration constants.
Usage
smuX.measure.calibrateY(range, cp1measured, cp1reference,
cp2measured, cp2reference)
range
cp1measured
cp1reference
cp2measured
cp2reference
2600S-901-01 Rev. C / January 2008
smuX.measure.autozero
The smuX.AUTOZERO_ONCE
X = SMU channel (a or b)
Y = SMU measure function (v or i)
where v = voltage, i = current
The measurement range to calibrate.
The value measured by this SMU for
calibration point 1.
The reference measurement for calibration
point 1 as measured externally.
T
he value measured by this SMU for calibration
point 2.
The reference measurement for calibration
measured externally.
Return to Section Topics
Section 12: Instrument Control Library
attribute can
setting can be
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