Tektronix KEITHLEY 2600B Series User Manual

Section 9: TSP command reference Series 2600B System SourceMeter® instrument Reference Manual
9-218 2600BS-901-01 Rev. F/August 2021
smuX.measure.autozero
This attribute enables or disables automatic updates to the internal reference measurements (autozero) of
the instrument.
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 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 automatically takes two more A/D conversions, one for the reference and one
for the zero, before returning the result. Thus, occasionally, a measurement takes more time 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.
Disabling automatic reference measurements may allow the instrument to gradually drift out of
specification. To minimize the drift, make a reference and zero measurement immediately 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 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 = smua.AUTOZERO_ONCE
Performs autozero once for SMU channel A.

Tektronix KEITHLEY 2600B Series Specifications

General

Brand	Tektronix
Model	KEITHLEY 2600B Series
Category	Measuring Instruments
Language	English