Keithley 2600B User Manual

Series 2600B
System SourceMeter® Instrument Reference Manual Section 7:
TSP command reference
2600BS-901-01 Rev. C / August 2016 7-215
smuX.measure.autozero
This attribute enables or disables of the internal reference measurements (autozero) of the source-measure unit.
Type TSP-Link accessible Affected by Where saved Default value
Attribute (RW)
Yes
Instrument reset
SMU reset
Recall setup
Saved setup
2 (smuX.AUTOZERO_AUTO)
Usage
azMode = smuX.measure.autozero
smuX.measure.autozero = azMode
azMode
Indicates status of autozero; set to one of the following values:
0 or smuX.AUTOZERO_OFF: Autozero disabled
1 or smuX.AUTOZERO_ONCE: Performs autozero once, then disables autozero
2 or smuX.AUTOZERO_AUTO: Automatic checking of reference and zero
measurements; an autozero is performed when needed
X
Source-measure unit (SMU) channel (for example, smua.measure.autozero
applies to SMU channel A)
Details
The analog-to-digital converter (ADC) uses a ratiometric A/D conversion technique. To ensure the
accuracy of readings, the instrument must periodically obtain new measurements of its internal
ground and voltage reference. The time interval between updates to these reference measurements
is determined by the integration aperture being used for measurements. The Series 2600B uses
separate reference and zero measurements 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 additional time can cause problems in sweeps and other test sequences in which measurement
timing is critical. To avoid the time that is needed for the reference measurements in these situations,
you can use the smuX.measure.autozero attribute to disable the automatic reference
measurements.
Remember that disabling automatic reference measurements may allow the instrument to gradually
drift out of specification. To minimize the drift, a reference and zero measurement should be made
just before any critical test sequences. You can use the smuX.AUTOZERO_ONCE setting to force a
refresh of the reference and zero measurements that are used for the present aperture setting.
The Series 2600B stores the reference measurements for the last ten NPLC settings that were used
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 is discarded to make room for the new entry.
Example
smua.measure.autozero = 1
Performs autozero once for SMU channel A. Alternatively,
the value 1 may be replaced with
smua.AUTOZERO_ONCE
.

Keithley 2600B Specifications

General

Brand	Keithley
Model	2600B
Category	Measuring Instruments
Language	English