Trigger Auto Level Mode

Controls: Trigger Dialog >> Auto Level
Macro: TrigMode=Alevel

With Auto Level the operation is similar to Auto, in that the trace is updated after 1024 samples without a trigger event. The difference is that the effective Trigger Level is scaled according to the peak signal of the prior update. This mode is similar to Auto Trigger on a conventional oscilloscope, if you are already familiar with that.

Suppose, for example, that Level is set to +500 mV on a +/-1 volt input range, or half of positive full scale. Then the actual trigger level will be at half of the zero-to-peak amplitude of the signal, and it will self-adjust as the input level changes... if the signal level is only 42 mV, then the effective trigger level will be 21 mV. This allows a stable trace under changing input conditions.

The Auto-trigger logic scans 1024 samples waiting for a valid trigger, based upon the current effective level set by the previous frame. If a trigger is not found, those 1024 samples are displayed anyway and used to compute the trigger level for the next frame. The waveform display may thus "hiccup" for one frame when the level drops suddenly.

A powerful advantage of Auto Level mode is that you thus always get a more-or-less ongoing frame display. This allows you to see what is going on, even when things are not happening the way you assumed when you set the original trigger Level.

Macro Notes:

TrigMode=ALevel or TrigMode=1 sets the mode to Auto Level. See Macro Notes under Trigger Auto Mode for the complete list of mode names and numbers.

See also Trigger Toggle - Introduction, Trigger Control Dialog