prog.book : ch2meas.fm 21 Mon Feb 15 09:24:37 1999
MEASurement Instructions
FETCh[1|2] Queries
HP E4418B/E4419B Programming Guide 2-21
FETCh[1|2] Queries
The FETCh? queries set the specified window’s measurement function 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 return is <NR3>, for example,
-6.98970004E-001.
The query returns a measurement result whenever it is valid. The
measurement result becomes 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 is 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.
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