Tektronix Keithley 2601B-PULSE Reference Manual

Model 2601B-PULSE System SourceMeter Instrument Reference Manual Section 11: TSP command reference
2601B-PULSE-901-01A April 2020 11-195
smua.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 (smua.AUTOZERO_AUTO)
Usage
azMode = smua.measure.autozero
smua.measure.autozero = azMode
azMode
Indicates status of autozero; set to one of the following values:
▪ 0 or smua.AUTOZERO_OFF: Autozero disabled
▪ 1 or smua.AUTOZERO_ONCE: Performs autozero once, then disables autozero
▪ 2 or smua.AUTOZERO_AUTO: Automatic checking of reference and zero
measurements; an autozero is performed when needed
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 2601B-PULSE 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 smua.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, a reference and zero measurement should be made immediately
before any critical test sequences. You can use the smua.AUTOZERO_ONCE setting to force a refresh
of the reference and zero measurements that are used for the present aperture setting.
The 2601B-PULSE 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.
When the pulser is enabled, two high-speed digitizing sampling ADCs are used to measure voltage
and current. These ADCs do not use a ratiometric conversion technique, so the autozero settings are
ignored when the pulser is enabled.
Example
smua.measure.autozero = smua.AUTOZERO_ONCE
Performs autozero once.

Tektronix Keithley 2601B-PULSE Specifications

General

Brand	Tektronix
Model	Keithley 2601B-PULSE
Category	Measuring Instruments
Language	English