Keysight Technologies 86120B, User Manual

Page: 148 / 273

146
Programming Commands
Measurement Instructions
Measurement Instructions
Use the measurement instructions documented in this section to perform measure-
ments and return the desired results to the computer. Four basic measurement
instructions are used: CONFigure, FETCh, READ, and MEASure. Because the
command trees for each of these four basic measurement instructions are identical,
only the MEASure tree is documented.
To perform a measurement, append to the measurement instruction a POWer or
LENGth function. The POWer functions select power, frequency, wavelength, or
wave number measurements. Use the LENGth functions to configure the instrument
to measure coherence length. The instrument measures the coherence length in the
time domain by rectifying and low-pass filtering the interferogram. The resulting
waveform is then curve fit into a decaying exponential.
Refer to “To measure coher-
ence length” on page 78 .
When the :SCALar command is used, data for a single measurement value is
returned. When the :ARRay command is used, multiple data values are returned.
The MEASure measurement instruction always acquires new measurement data. In
order to obtain both wavelength and power values from the same measurement data,
use two FETCh commands. This is shown in the following program 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. You can also send a
MEASure command followed by a FETCh command.