Measurement Queries; Fetch - Keithley 2750 User Manual

Model 2750 Multimeter/Switch System User's Manual
Example #4 – Scan configuration (Model 7700)
The following commands configure scan channels 101, 102, and 121 of a Model 7700
installed in slot 1. When channel 101 is scanned, DCV will be selected. When channel 102
is scanned, Ω2 will be selected. When channel 121 is scanned, DCI will be selected.
FUNC 'VOLT',(@101)
FUNC 'RES',(@102)
FUNC 'CURR',(@121)
NOTE

Measurement queries

NOTE

:FETCh?

What it does
This command will simply return the latest available reading from an instrument.
Limitations
If the instrument does not have a reading available (indicated by dashes in the display),
sending this command will cause a –230, "Data corrupt or stale" error. This query will not
cause the box to trigger a reading, nor will it "wait" for a result if a reading is in progress.
It is possible to get the same reading over and over using this query. It will continue to give
the same result until one of two things has happened:
•
•
Where appropriate
Since this query does not trigger a reading and can give duplicate results, there are not many
cases where this command should be used. The :DATA:FRESh? query
often a better choice. If this query is used, the following conditions should be met:
•
•
Detailed information on scanning is provided in
For more information on read commands, see Section 8
13 (SCPI Signal Oriented Measurement Commands) and Appendix D (Signal
Processing Sequence and Data Flow).
A new reading has been triggered
The old reading has been invalidated by changing ranges or by changing function.
A reading has been triggered, by either free running (:INIT:CONT ON and
:TRIG:SOUR IMM), by some event such as a bus trigger (*TRG), or by an exter-
nal trigger (:TRIG:SOUR EXT).
It is confirmed that the reading is completed by either the setting of the RAV bit in
the status model or by allowing sufficient time to pass for the reading to complete.
' Configure scan channel 101 for DCV.
' Configure scan channel 102 for Ω2.
' Configure scan channel 121 for DCI.
Basic DMM Operation
Section 7.
(see page 3-50), Section
(see page 3-52)
3-49
is