Several of the voltage measurements require threshold and edge information
before they can be made.
•
Vavg cycle = average voltage of the first cycle of the signal
•
Vavg = average voltage of all data on the display
•
dc Vrms =
√
(
v
(
t
))(
v
(
t
))
⁄
n
•
ac Vrms =
√
(
v
(
t
)−
Vavg
)(
v
(
td
)−
Vavg
)
⁄
n
•
Overshoot = a distortion which follows a major transition
If first edge is rising
then overshoot = local max
−
top
else overshoot = base
−
local min
•
Preshoot = a distortion which precedes a major transition
If first edge is falling
then preshoot = base
−
local min
else preshoot = local max
−
top
The oscilloscope computes a local minimum and maximum when computing
preshoot and overshoot. The local minimum or maximum occurs before the
first transition in the case of preshoot or in the first 50 percent of the time
defined along the threshold in the case of overshoot. This makes windowing
less critical for these measurements.
Measurements
Voltage Measurements
13–15
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