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:READ command
The READ command works like the MEASure com-
mand except that it does not configure the settings of
the instrument. You can use the CONFigure command
to configure the instrument for a particular measure-
ment without returning any data.
The MEASure and READ commands are identical to
combining the following commands:
Command
:MEASure
:READ
A common programming error is to send the :READ
command when the instrument is in the continuous
measurement acquisition mode. Because :READ con-
tains an :INIT:IMM command, which expects the single
measurement acquisition mode, an error is generated,
and the INIT command is ignored.
:FETCh command
The FETCh command returns data from previously per-
formed measurements; it does not initiate the collection
of new data. Because FETCh does not configure the
instrument or acquire new input data, you can use
FETCh repeatedly on the same set of acquired data.
For example, use two FETCh commands to return
wavelength and then power values for the same mea-
surement. This is shown in the following program frag-
ment:
OUTPUT 720;":INIT:CONT OFF;"
OUTPUT 720;":CONF:ARR:POW MAX"
OUTPUT 720;":INIT:IMM"
OUTPUT 720;":FETC:ARR:POW?"
ENTER 720:powers$
OUTPUT 720;":FETC:ARR:POW:WAV?"
ENTER 720:wavelengths$
In the example above, the data in the power and wave-
length arrays are returned in the same order so that
powers can be matched to wavelengths.
Also, because new data is not collected, FETCh is espe-
cially useful when characterizing transient data.
Making Measurements
Equivalent Commands
:ABORt;:CONFigure;:READ
:ABORt;:INITiate:IMMediate;:FETCh
4-9
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