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Programming
Making Measurements
A common programming error is to send the :MEASure command when the instru-
ment is in the continuous measurement acquisition mode. Because :MEASure con-
tains an :INIT:IMM command, which expects the single measurement acquisition
mode, an error is generated, and the INIT command is ignored.
:READ command
The READ command works like the MEASure command except that it does not
configure the instrument's settings. You can use the CONFigure command to con-
figure the instrument for a particular measurement without returning any data.
The MEASure and READ commands are identical to combining the following com-
mands:
Command
Equivalent Commands
:MEASure
:ABORt;:CONFigure;:READ
:READ
:ABORt;:INITiate:IMMediate;:FETCh
A common programming error is to send the :READ command when the instrument
is in the continuous measurement acquisition mode. Because :READ contains 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 performed 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 measurement. This is shown in the following pro-
gram fragment:
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 wavelength arrays are returned in
the same order so that powers can be matched to wavelengths.
Also, because new data is not collected, FETCh is especially useful when character-
izing transient data.
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