
Considerations for Changing the Minimum Number of Averages
The default Minimum Average values have been selected so that the
measurement time for each Measurement Range is approximately equal
to the time it takes to process and plot the data taken during the previous
measurement.
Increasing the number of averages reduces the scatter of the points around
the true noise; however, it may also increase the time it takes to complete
the measurement.
The following equations can be used to compute the measurement time
using the greater of the two Minimum Average values.
For HP 3561A Spans < 5 kHz:
Time Record Length
Measurement Time = (1 + Min. Avg) x
For HP 3561A Spans > 5 kHz:
Measurement Time
—
Min. Avg. x 60msec
Bandwidth
The Bandwidth is automatically set by the HP 3048A to the appropriate
value for each Measurement Range. The Bandwidth is determined by
the Frequency Span setting of the HP 3561A. The Bandwidth value is
approximately 1% of the HP 3561 A's span setting. (Note that this is not
the same as display resolution which is 0.25% of the span setting).
5-16 FFTSegmnts
reu.22SEP89
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