Operation Manual

Model 2750 Multimeter/Switch System User’s Manual Basic DMM Operation 3-47
DATA:FRESh? can only be used once to return the same reading string. That
is, the reading must be “fresh.” Sending this command again to retrieve the
same reading string will generate error -230 (data corrupt or stale), or cause a
the GPIB to time-out. In order to again use DATA:FRESh? a new (fresh) read-
ing must be triggered.
FETCh?
READ?
FETCh? is similar to DATA[:LATest]]? in that it can be used to return the last
reading. However, it can also be used to return more than one reading. When
returning more than one reading, the readings are automatically stored in the
buffer.
In order to return multiple reading strings, continuous initiation must be dis-
abled (INIT:CONT OFF) so that the sample count (SAMPle:COUNt), which
specifies the number of measurements to be performed, can be set >1. After
INITiate is sent to trigger the measurements, FETCh? will return the reading
strings.
In general, READ? performs an INIT to trigger measurements and then a
FETCh? to retrieve the reading strings. With continuous initiation disabled
(INITiate:CONTinuous OFF), you can use the READ? command to trigger
and return readings. The sample count determines the number of reading
strings to be returned. With the sample count >1, the returned readings are
automatically stored in the buffer.
NOTE When readings are stored in the buffer by the TRACe command (or
by front panel data store operation), INIT and multi-sample READ?
queries are locked out. With readings in the buffer that were stored
in that manner, you cannot use the INIT or READ? command if sam-
ple count is >1 (error -225, out of memory). Buffer operation is cov-
ered in Section 6.
2750-900-01.book Page 47 Wednesday, August 3, 2011 7:56 AM