Oscilloscope Reference Measurement algorithms
Delay
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.
Extinction ratio
Optical measurement between 1 and 100. In real circuits, the extinction ratio is typically 8 to 30. Values
≤ 1or≥ 100 generate errors. An Extinction Ratio of 1 or 100 means a problem exists. The optical probe
and the i
nstrument must b e calibrated. All inputs are micro watts and are not negative. Extinction ratio
is dimensionless.
Extinc
tion Ratio = (High/Low)
Low ≥ 1 μW
Extinction %
Opti
cal measurement.
Extinction % = 100.0 / Extinction Ratio
Extinction dB
Opt
ical measurement. Extinction dB is typically 8 to 12 db. To exceed this range the input m ay be from
nonoptical probes or noncommunication lasers.
Ex
tinction dB = 10.0 (log
10
(Extinction Ratio))
Fall time
fall time
Timing measurement. The time taken for the falling edge of a pulse to drop from a HighRef value (default
=90%)toaLowRef value (default = 10%).
The following figure shows a falling edge with the two crossings necessary to calculate a Fall measurement.
1. Searching from Start to End, find th e 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 nec essary.)
DSA/DPO70000D, MSO/DPO/DSA70000C, DPO7000C, and MSO/DPO5000 Series 731
To Next Page
Loading...
Need help?
General
