Tektronix DPScope II, User Manual

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Short description of each measurement:

Low : lowest value (minimum) on the screen.

High : highest value on the screen.

Mid : Midpoint between low and high, mid = (low + high) / 2

DC mean : average voltage level, calculated over all points on the screen

Amplitude : difference between high and low, amplitude = high
– low

AC RMS : RMS value calculated with the midlevel taken as the reference

Rise time : time to rise from 10% to 90% of the swing (low = 0%, high = 100%)

Fall time : time to fall from 90% to 10% of the swing (low = 0%, high = 100%)

Period : time between subsequent rising edges crossings of the 50% point (midlevel) (or
falling edges if there aren’t two rising edges on the screen)

Frequency : 1/period

Duty cycle : time spent above 50% during one period, relative to the length of the period.
duty_cycle = pos. width / period

Pos. width : time spent above 50% during one period

Neg. width : time spent below 50% during one period
The threshold drop-down selection box lets you select which set of levels the measurements
shall use for rise time and fall time measurements
– either 10% (start of rising egde / end of
falling edge) and 90% (start of falling egde / end of rising edge) of the full swing, or 20% and
80%, respectively.
2.8.2 Spectrum Analysis