User's Manual

Appendix B: Algorithms
B–8
TDS 500C, TDS 600B, & TDS 700C User Manual
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.
Optical measurement.
Extinction Ratio = (High/Low)
Optical measurement.
Extinction % = 100.0 / Extinction Ratio
Optical measurement.
Extinction dB =  

 
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 .
2. From this sample, continue the search to find the first (negative) crossing of
. The time of this crossing is . (Use linear interpolation if
necessary.)
Delay
Extinction Ratio
Extinction %
Extinction dB
Fall Time