Smoothing filters. These are sometimes called box car filters. They simply average together adjacent samples along the time
record. The filter coefficients for these filters are all equal to 1/ M where M is the length of the filter. The name of the files
indicates the length of the smoothing filter.
Smoothing filters are low pass filters with a somewhat less than optimal stop band characteristic. However, they are commonly
used to remove high frequency noise from a displayed trace. Take care in using to insure that the pass band of the signal you are
filtering is well within the pass band of the filter you choose. That will insure that only noise is removed. Lengths of 3, 5, 10, 20,
50, 100, and 200 are provided in the library. The red trace is for filter length 3, followed by blue trace at 5, followed by magenta
trace for 10, and so on.
Figure 28: Frequency response of the available smoothing filters
The following table lists the available smoothing filters:
File name Length Normalized bandwidth Stop band attenuation dB
smooth3.flt 3 0.1558 -9.4
smooth5.flt 5 0.0903 -12
smooth10.flt 10 0.0446 -12.9
smooth20.flt 20 0.0224 -13.2
smooth50.flt 50 0.00887 -13.2
smooth100.flt 100 0.0045 -13.2
smooth200.flt 200 0.0022 -13.2
Oscilloscope reference
790 DPO70000SX, MSO/DPO70000DX, MSO/DPO70000C, DPO7000C, and MSO/DPO5000B Series
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