I'm currently designing something that requires an adjustable scroll wheel mechanism like the one on this active probe. Unfortunately, I don't have the device myself to examine.

Would anyone be able to suggest similar mechanisms or explain how this particular scroll wheel might work? Any insights would be greatly appreciated! active probe work?

enter image description here

  • $\begingroup$ It appears that you are asking how the wheel functions, although your question is "how does the probe work?" I suggest an edit to remove the ambiguity. $\endgroup$
    – fred_dot_u
    Commented Feb 7 at 9:52
  • 1
    $\begingroup$ examine a drafting compass ... walmart.com/ip/… $\endgroup$
    – jsotola
    Commented Feb 7 at 16:36

1 Answer 1


Presuming that your focus is the scroll wheel, there are a couple of methods in which one can read a scroll wheel of this nature.

The sides of the wheel could have a reflective pattern, which would be detected and measured by an optical sensor. The pattern could be counted in a manner similar to a rotary encoder.

The wheel's axle could pass through a bearing or similar support and be connected to a rotary encoder.

Variations of the above include having the axle spin a disk with either reflective patterns or optical slots with suitable detectors. The wheel could have slots through which an optical sensor would detect a beam make/break as the wheel rotates.


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