D-10 Signal Processing Sequence and Data Flow Model 2750 Multimeter/Switch System User’s Manual
NOTE For more information on FETCh?, READ? and MEASure?, see Section 13,
“SCPI Signal Oriented Measurement Commands.”
FETCh?
With no Math function enabled, this command reads the data arrays stored in the sample
buffer. If, for example, there are 20 data arrays stored in the sample buffer, then all 20 data
arrays will be sent to the computer when FETCh? is executed.
With a Math function (mX+B, Percent, or 1/X) enabled, the reading in each data array
returned by FETch? is the result of the math calculation.
Note that FETCh? does not affect data in the sample buffer. Therefore, subsequent execu-
tions of FETCh? acquire the same data.
NOTE When an instrument setting that is relevant to the readings in the sample buffer
is changed, the FETCh? command will cause error -230 (data corrupt or stale)
or a bus time-out to occur. To get FETCh? working again, a new reading must
be triggered.
READ?
The READ? command performs an INITiate and then a FETCh? The INITiate triggers a
measurement cycle which puts new data in the sample buffer. With no Math function
enabled, FETCh? reads the data arrays from the sample buffer. With a Math function
enabled, the readings are the result of the math calculation.
The following conditions must be met in order to use READ?:
• Continuous initiation must be disabled. It can be disabled by sending *RST or
INIT:CONT OFF.
• If there are readings stored in the data store, the sample count (SAMP:COUN)
must be set to 1.
• To use a sample count >1, the data store must be cleared (empty). It can be cleared
by sending TRAC:CLE.
MEASure?
The MEASure? command places the instrument in a “one-shot” measurement mode
(which places one data array in the sample buffer) and then performs a READ?. With no
Math function enabled, the one data array in the sample buffer is read. With a Math func-
tion enabled, the reading is the result of the math calculation.
2750-900-01.book Page 10 Wednesday, August 3, 2011 7:56 AM
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