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Appendix B: Algorithms
TDS 620A, 640A & 644A User Manual
AĆ15
Negative Width
Timing measurement. The distance (time) between MidRef (default = 50%)
amplitude points of a negative pulse.
If MCross1Polarity = `-'
then
NegativeWidth = (MCross2 - MCross1)
else
NegativeWidth = (MCross3 - MCross2)
Peak to Peak
Amplitude measurement. The absolute difference between the maximum
and minimum amplitude.
PeaktoPeak = Max - Min
Period
Timing measurement. Time taken for one complete signal cycle. The recipĆ
rocal of frequency. Measured in seconds.
Period = MCross3 - MCross1
Phase
Timing measurement. The amount of phase shift, expressed in degrees of
the target waveform cycle, between the MidRef crossings of two different
waveforms. Waveforms measured should be of the same frequency or one
waveform should be a harmonic of the other.
Phase is a dual waveform measurement; that is, it is measured from a target
waveform to a reference waveform. To get a specific phase measurement,
you must specify the target and reference sources.
Phase is determined in the following manner:
1. The first MidRefCrossing (MCross1Target) and third (MCross3) in the
source (target) waveform are found.
2. The period of the target waveform is calculated (see Period" above).
3. The first MidRefCrossing (MCross1Ref) in the reference waveform crossing
in the same direction (polarity) as that found MCross1Target for the target
waveform is found.
4. The phase is determined by the following:
Phase =
MCross1Ref * MCross1Target
Period
360