Oscilloscope triggers unexpectedly when horizontal scale is large

by Annie   Last Updated May 03, 2018 01:25 AM

When I set the horizontal axis to something large (40ms/div or greater) and hit the Single button, the scope triggers immediately, although no trigger has occurred. I tried the following:

  • Setting the trigger to something ridiculously high and grounding the channel that it triggers on, to make sure that noise was not triggering it. It still triggered immediately.
  • Setting the horizontal scale to 20ms/div, hitting the Single button, and then increasing to 40ms/div. This worked; i.e. did not trigger until the trigger actually occurred.

I am using a Tektronix MSO54, but I also recall observing this phenomenon on another scope in the past. This has got to be something obvious, but for the life of me I can't figure out what.

Tags : oscilloscope

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