Tektronix TDS 500B - Page 253

Appendix B: Algorithms
B–12
TDS 500B, TDS 600B, & TDS 700A User Manual
The integration algorithm used by the oscilloscope is as follows:
ŕ
B
A
W(t)dt
is approximated by
ŕ
B
A
W
^
(t)dt
where:
W(t) is the sampled waveform

^
()
is the continuous function obtained by linear interpolation of W(t)
A and B are numbers between 0.0 and –1.0
If A and B are integers, then:
ŕ
B
A
W
^
(t)dt + s
ȍ
B*1
i+A
W(i) ) W(i ) 1)
2
where s is the sample interval.
Similarly,
ŕ
B
A
(
W(t)
)
2
dt
is approximated by
ŕ
B
A
ǒ
W
^
(t)
Ǔ
2
dt
where:
W(t) is the sampled waveform

^
()
is the continuous function obtained by linear interpolation of W(t)
A and B are numbers between 0.0 and –1.0
If A and B are integers, then:
ŕ
B
A
ǒ
W
^
(t)
Ǔ
2
dt + s
ȍ
B*1
i+A
(
W(i)
)
2
) W(i) W(i ) 1) )
(
W(i ) 1)
)
2
3
where s is the sample interval.
Measurements on Envelope Waveforms
Time measurements on envelope waveforms must be treated differently from
time measurements on other waveforms, because envelope waveforms contain so
many apparent crossings. Unless otherwise noted, envelope waveforms use either
the minima or the maxima (but not both), determined in the following manner:
1. Step through the waveform from  to  until the sample min and max
pair DO NOT straddle .
2. If the pair > , use the minima, else use maxima.
Integration Algorithm