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  =  then return the (interpolated) value at .
= ŕ

()dt
( *) 
For details of the integration algorithm, see page B–12.
The true Root Mean Square voltage over one cycle.
If  =  then  = .
Otherwise,
 = ŕ

(())2dt
( *) 
Ǹ
For details of the integration algorithm, see page B–12.
Timing measurement. The amount of time between the  and 
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.
 = the time from one  crossing on the source waveform to the
 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  value (default = 90%) to a  value (default = 10%).
Figure B–2 shows a falling edge with the two crossings necessary to calculate a
Fall measurement.
1. Searching from  to , find the first sample in the measurement zone
greater than .

Cycle Mean

Cycle RMS

Delay

Fall Time