Chapter 10
Triggering
©
National Instruments Corporation
10-5
Level Triggering with Hysteresis
Hysteresis adds a programmable window above or below the trigger level
that a valid trigger signal must pass through and is often used to reduce
false triggering due to noise or jitter in the signal.
When using
Hysteresis
with a rising slope, the trigger asserts when the
signal starts below
Level
and then crosses above
Level
. The trigger
deasserts when the signal crosses below
Level
minus hysteresis as shown
in Figure 10-5.
Figure 10-5.
High Hysteresis
When using
Hysteresis
with a falling slope, the trigger asserts when the
signal starts above
Level
and then crosses below
Level
. The trigger
deasserts when the signal crosses above
Level
plus hysteresis, as shown in
Figure 10-6.
Low Hysteresis
Window Triggering
A window trigger occurs when an analog signal either passes into (enters)
or passes out of (leaves) a window defined by two voltage levels. Specify
the levels by setting the window
Top
value and the window
Bottom
value.
Level
Analog Comparison Event
Hysteresis
Level
Analog Comparison Event
Hysteresis