2 MEASurement Commands
110 N1911A/1912A P-Series Power Meters Programming Guide
FETCh[1]|2|3|4 Queries
The FETCh? queries set the specified window’s measurement function. This
can be set to either single channel, difference or ratio measurements, with
relative mode either off or on. They then recalculate the measurement and
place the result on the bus. The format of the result is set by
FORM[:READ][:DATA]. Refer to Chapter 6, “FORMat Subsystem,” on page
249 for further information.
The query returns a measurement result when it is valid. The
measurement result is invalid under the following conditions:
•When *RST is executed.
• Whenever a measurement is initiated.
•When any SENSe parameter, such as frequency, is changed.
If data is invalid, the FETCh? query is not completed until all data
becomes valid. The exceptions to this are, if the power meter is in the idle
state and the data is invalid, or the power meter has been reconfigured as
defined above and no new measurement has been initiated. In such cases,
the FETCh? routine generates the error –230, “Data corrupt or stale” and
no result is returned. A common cause for this error is receiving a FETCh?
after a *RST. If the expected value and resolution parameters are not the
same as those that were used to collect the data, error –221, “Settings
conflict” occurs.
When TRIG:SOUR is INT1, INT2 or EXT and a new acquisition has been initiated (using the
INIT command for example), FETCH? waits until the trigger takes place before executing. If triger
conditions are not satisfied - when the trigger level differs greatly from the signal level for example -
this can give the impression that the power meter has hung.
To unlock the power meter and adjust trigger settings, an SDC (Selected Device Clear) GPIB
Command must be performed. This is equivalent to “EXECUTE CLEAR” in Agilent VEE.
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