At/Norm
Using the "At/Norm" button you can switch between Automatic trigger level selection (At) and Normal (manual) trigger level. The trigger level in automatic mode is the level during 0v crossing. The trigger level in manual mode can be set using the "Level" control located below "At/Norm." Using that control, voltages larger than the amplitude of the signal can be set, too. However, as the signal level will never reach that trigger level, the signal will not be triggered in that case.
To make sure the simulation allows demonstration of this
function even for high input voltages, an algorithm has been
implemented that does not use the voltage of a signal: In the
simulation a signal is always triggered as long as the trigger
control
is rotated within a range of -90° and +90° from its center position,
outside this range it is not triggered.
In reality the maximum
trigger level would equal 100%, and the trigger range would be
based on the true voltage of the signal.
For small
input voltages on a real oscilloscope minor moves of the control
will
influence the trigger level. Small movements cannot be
executed by the simulation using the mouse.
A signal can be triggered on the ascending or descending part of the
waveform by using the "+/-"