Model 2651A High Power System SourceMeter® Instrument Reference Manual
Section 2: General operation
2651A-901-01 Rev. A / March 2011
2-23
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 OFF
selection can be used to disable the automatic reference measurements. Note 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. The ONCE setting can be used to force a refresh of the reference and zero measurements
used for the current aperture setting.
Autozero settings
Autozero setting
Description
OFF
Turns automatic reference measurements off.
ONCE
Turns automatic reference measurements off, but immediately taking one
reference and one zero measurement.
AUTO
Automatically takes new acquisitions when processor determines
reference and zero values are out-of-date.
Front-panel autozero
Set the autozero from the front panel as follows:
1. Press
the
CONFIG
key, and then press the
MEAS
key.
2. Turn the navigation wheel
to select
AUTO-ZERO
, and then press the
ENTER
key or the
navigation wheel
.
3. Turn the navigation wheel
to select the desired mode (
OFF
,
ONCE
, or
AUTO
), and then press
the
ENTER
key or the navigation wheel
.
4. Press
the
EXIT (LOCAL)
key to return to the normal display.
Remote command autozero
Use the autozero command with the appropriate option shown in the following table to set autozero
through a remote (see
(on page 7-192) for more details). For example, send
the following command to activate channel A automatic reference measurements:
smua.measure.autozero = smua.AUTOZERO_AUTO
Autozero command and options
Command Description
smua.measure.autozero = smua.AUTOZERO_OFF
Disable autozero**
smua.measure.autozero = smua.AUTOZERO_ONCE
Force one ref and zero
smua.measure.autozero = smua.AUTOZERO_AUTO
Reacquire ref and zero with
measurement when needed
**Old NPLC cache values will be used when autozero is disabled (see
