Tektronix, Inc. P6240, User Manual

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Appendix B: Algorithms
B–6
TLS 216 User Manual
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
.
2. From this sample, continue the search to find the first (negative) crossing of
HighRef
. The time of this crossing is
THF
. (Use linear interpolation if
necessary.)
3. From
THF
, continue the search, looking for a crossing of
LowRef
. Update
THF
if subsequent
HighRef
crossings are found. When a
LowRef
crossing is
found, it becomes
TLF
. (Use linear interpolation if necessary.)
4.
FallTime
=
TLF
–
THF
Delay
Fall Time