Appendix B: Algorithms
B–6
TDS 684A, TDS 744A, & TDS 784A User Manual
Amplitude (voltage) measurement. The mean over one waveform cycle. For
non-cyclical data, you might prefer to use the Mean measurement.
If StartCycle = EndCycle then return the (interpolated) value at StartCycle.
CycleMean=
ŕ
EndCycle
StartCycle
Waveform(t)dt
(EndCycle * StartCycle) SampleInterval
For details of the integration algorithm, see page B–12.
The true Root Mean Square voltage over one cycle.
If StartCycle = EndCycle then CycleRMS = Waveform[Start].
Otherwise,
CycleRMS =
ŕ
EndCycle
StartCycle
(Waveform(t))
2
dt
(EndCycle * StartCycle) SampleInterval
Ǹ
For details of the integration algorithm, see page B–12.
Timing measurement. The amount of time between the MidRef and Mid2Ref
crossings of two different traces, or two different places on the same trace.
Delay measurements are actually a group of measurements. To get a specific
delay measurement, you must specify the target and reference crossing polarities
and the reference search direction.
Delay = the time from one MidRef crossing on the source waveform to the
Mid2Ref crossing on the second waveform.
Delay is not available in the Snapshot display.
Timing measurement. The time taken for the falling edge of a pulse to drop from
a HighRef value (default = 90%) to a LowRef value (default = 10%).
Figure B–2 shows a falling edge with the two crossings necessary to calculate a
Fall measurement.
1. Searching from Start to End, find the first sample in the measurement zone
greater than HighRef.
Cycle Mean
Cycle RMS
Delay
Fall Time
