prog.book : chapter1.fm 68 Mon Feb 15 09:24:37 1999
Power Meter Remote Operation
Getting the Best Speed Performance
1-68 HP E4418B/E4419B Programming Guide
For example, with a filter length of 4 and SENS:SPE set to 20,
approximately 5 readings/sec will be calculated by the power meter.
In general, free run mode will provide the best speed performance from
the power meter (especially in 200 readings/sec mode).
Output Format
The power meter has two output formats for measurement results: ASCii
and REAL. These formats can be selected using the FORMat command.
When FORMat is set to REAL, the result returned is in IEEE 754
floating-point format (note that the byte order can be changed using
FORMat:BORDer).
The REAL format is likely to be required only for 200 readings/sec mode as
a means to reduce bus traffic.
Units
The power meter can output results in either linear or log units. The
internal units are linear and therefore optimal performance will be
acheived when the results output are also in linear units (since the
overhead of performing a log function is removed).
Command Used
In free run trigger mode, FETC? must be used to retrieve a result.
In other trigger modes, there are a number of commands which can be
used, for example, MEAS?, READ?, FETC? Note that the MEAS? and
READ? commands are compound commands i.e., they perform a
combination of other lower level commands. In general, the best speed
performance will be achieved using the low level commands directly.
200 Readings/Sec
In the highest speed setting, the limiting factor tends to be the speed of
the controller being used to retrieve results from the power meter and to a
certain extent the volume of HP-IB traffic. The latter can be reduced using
the FORMat REAL command to return results in binary format. The
former is a combination of two factors:
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