Keithley 6482, Справочное руководство

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6482-901-01 Rev. A / August 2012 Return to Section Topics 15-3
Model 6482 Dual-Channel Picoammeter / Voltage Source Reference Manual Section 15: SCPI Measurement Commands
Acquiring readings
This topic describes commands to acquire post-processed readings, both trigger and acquire
readings, and to perform a single measurement.
FETCh?
Description This query command requests the latest post-processed readings stored in the
sample buffer. After sending this command and addressing the Model 6482 to
talk, the readings are sent to the computer. This command does not affect the
instrument setup.
This command does not trigger source and measure operations; it requests the
last available readings. Note that this command can repeatedly return the same
readings. Until there are new readings, this command continues to return the old
readings. For example, assume that the Model 6482 performed 20 source and
measure operations. The :FETCh? command will request the readings for those
20 source and measure operations. If :FETCh? is sent while performing source
and measure operations (ARM indicator on), it will not be executed until the
Model 6482 goes back into an idle state.
NOTE
The :FETCh? command is automatically asserted when the :READ? or :MEASure?
command is sent.
The readings that are acquired depend on which data elements are selected
(
Section 16 , “FORMat subsystem,” “Data elements” ). Measure readings take
priority over source readings, and data from channels not sourced or measured
are assigned the NAN (not a number) value of +9.91e37.
NOTE
Send :FORM:ELEM CURR1 before :FETCh? for channel 1 readings or :FORM:ELEM
CURR2 for channel 2 readings.
See Appendix B for a detailed explanation on how data flows through the various
operation blocks of the Model 6482 . It clarifies the types of readings that are acquired by
the commands to read data.
DATA[:LATest]?
Description This command works exactly like FETCh?, except that it returns only the most
recent reading from the channel selected by :FORM:ELEM.