Quote Originally Posted by curious aardvark View Post
the device uses an adhesize magnetic strip that attaches to the print head. The measurer then magnetically attaches to the strip.
ie: no ferrous parts are needed. I've gota roll of magnetic sticky tape in my workshop, useful stuff.

So if the device doesn't need to line up with the printhead - how can you know how far the printhead is from the bed.
I know I'm labouring this point - but I just don't see how it works.
The same way that you use an IR sensor or inductive proximity sensor. For bed leveling the offset donot matter. althpugh, it is important for zeroing.
Obviously, alignG doesn’t know the coordinates of the print head. Through trial and error, only for the first time, you find the best extruder/bed gap; then mount and leave alignG in that spot. You also reset the alignG reading in the software for that position.