Tektronix TDS 500C User Manual

Appendix B: Algorithms

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.

(High/Low)

Optical measurement.

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.)