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5 Portable FES System
77
Setting the Trigger Criteria
A general trigger module detects the trigger criterion in the interaction input signal. The
module is able to distinguish different signal patterns in the interaction input signal.
Two trigger levels, the signal slopes (positive or negative) at the trigger level cross
point, the time duration between the two trigger level cross points, and the above or
below threshold time duration are used as criterion to classify the different trigger
patterns. Figure 34 shows the GUI that is used to set the ten trigger parameters. One can
see graphically the two trigger levels and the three time duration. With these trigger
parameters sensor signal patterns consisting of maximum two peaks or two valleys can
be distinguished.
Figure 34: All parameters of a trigger criterion can be entered either numerically or graphically.
Additionally, the trigger criterion can be stored or loaded.
The following ten parameters have to be defined in order to detect a signal with two
peaks or two valleys:
1. level 1: Sets the trigger level (threshold) of the first peak (above threshold) or
valley (below threshold)
2. peak/valley 1: Sets the above or below threshold condition for level 1
3. time 1: Sets the time that the signal has to be above or below threshold of level 1
4. shorter/longer 1: Defines if the sensor signal has to be shorter or longer above
or below level 1 than time 1