User`s guide

7
4.4 Limits
The over and under limits checking functions used
in the 438A perform exactly the same way in the
E4419A/B. The only function that the E4419A/B
does not support is the “over high limit” and
“under low limit.” This is because the E4419A/B
does not allow the high limit threshold to be less
than the lower limit threshold, which this particu-
lar function requires. Software using this feature
will require a work around.
The 437B and 438A allow upper and lower limits
of +/-299.99 dBm while the EPM series power
meter restricts the lower limit to -150 dBm and
the upper limit to +230 dBm. Entries out of this
range will be accepted but truncated.
After a remote preset, the low limit will be set to
-0.001 dBm and the upper limit to 0.0 dBm.
4.5 Filter
The digital averaging filter in the EPM series power
meter ranges from 1 to 1024, while the maximum
averaging on the 437B and 438A is 512. Using
437B/438A language mode, the maximum number
of averages allowed in the EPM series power meter
is 512. If 1024 averages was selected prior to enter-
ing 437B/438A language, then this will automati-
cally be reduced to 512.
Note that in 437B/438A language mode, front
panel operation will not allow 1024 averages to
be selected.
With auto filter enabled, the filter setting selected
may differ from that in the 437B or 438A. The set-
ting selected by the EPM series power meters is
explained in the EPM series Programming Guide
under SENSe:AVERage:COUNt:AUTO.
4.6 Duty cycle, window offsets, sensor calibration tables,
and frequency dependent offset tables
Window offsets and frequency dependent offset
(FDO) tables are not available on the 437B or
438A but are features on the EPM series power
meter. The duty cycle feature and sensor calibra-
tion tables are not available on the 438A but are
on the E4419A/B. In general, the EPM series power
meter’s instrument state is not altered when the
437B/438A language is selected. Therefore, prior
to entering 437B/438A language, should any of
these features be enabled, they will then remain so
until a remote preset command is issued. This is
also the case with a local-to-remote transition with
437B/438A language selected. An explanation for
unexpected results or behavior may well be due to
having one of these features unknowingly enabled.
At the start of an application program a preset
command is worth considering, as this will ensure
that the EPM series power meter is in a known state.
Note: A front panel preset does not disable a selected
sensor cal table or FDO table.