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Model 2657A High Power System SourceMeter® Instrument Reference Manual
Section 7: TSP command reference
2657A-901-01 Rev. B/December 2012
7-195
Also see
(on page 7-211)
smuX.measure.autozero
This attribute sets the behavior of the SMU as to when it acquires reference measurements.
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
= smu
X
.measure.autozero
smu
X
.measure.autozero =
azMode
azMode
Indicates status of autozero; set to one of the following values:
0
or
smu
X
.AUTOZERO_OFF
: Autozero disabled
1
or
smu
X
.AUTOZERO_ONCE
: Performs autozero once, then disables autozero
2
or
smu
X
.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 integrating 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 Model 2657A 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
smu
X
.measure.autozero
attribute to disable the automatic reference measurements.
Содержание 2657A
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