Stanford Research Systems SR785, Руководство по эксплуатации и программированию

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Average Menus 4-111
SR785 Dynamic Signal Analyzer
Peak Hold Averaging
Peak hold averaging is similar to RMS averaging, in that the RMS measurement
quantities are calculated. However, instead of averaging the RMS measurements
together, in peak-hold averaging the new data is compared to the old data and the
maximum value is kept.
In Continuous Peak-Hold Averaging, the new data is continually compared with the
current maximum. In Fixed-Length PeakHold Averaging, a fixed number of records is
examined for the maximum.
Time Record Increment
Set the Time Record Increment for the active display [0% .. 300%]. The Time Record
Increment is how far the start of each time record is advanced between measurements (as
a percentage of the time record length).
If the increment is 100%, the start of the next time record is exactly one time record
advanced from the start of the previous time record.
If the increment is 25%, then the next time record starts 1/4 of a time record advanced
from the start of the previous time record. This is sometimes referred to as 75% overlap
since the two time records share 75% of a record. The overlap is simply 100% minus the
Time Record Increment.
When the Time Record Increment is less than or equal to 100%, the measurement is said
to be ‘real time’. All time points contribute to one (or more) measurements.
If the increment is 200%, the start of the next time record is advanced from the start of
the previous time record by 2 time records leaving a gap of 1 record. This means that the
data between the two time records is not measured.
When the Time Record Increment is greater than 100%, then the measurement is not
‘real time’ and some time points do not contribute to a measurement.
The actual time record increment for the measurements in progress is displayed in the
Real Time indicator in the status area (below the Input Ranges). If the indicator shows a
value greater than the requested Time Record Increment, it means that the measurement
cannot be made with the requested increment but is running with the smallest increment
possible. Factors which affect the processor’s ability to run real time include the
measurement type, averaging and source type.
Be sure to set the Time Record Increment to 100% when vector averaged measurements
are being used.
The Time Record Increment is ignored whenever the measurement is triggered. In this
case, the time records start with the trigger.
Settling
When the frequency span or input signal path (gain, filtering, etc.) is changed, a settling
time is required before the FFT measurement is considered settled or valid. The