I have just purchased one of the popular short scale units much like the electronic verniers etc. to fit to my lathe saddle and then with a quick release clamp to the bed so that I can have accurate bed travel measurement for putting accurate shoulders on or parting off to length and the like and I realise looking at it that there is no apparent connection, mechanical or optical between the moving display head and the fixed printed scale bar, so how does it pick up its measurement?
I would have thought if it was a friction drive in the moving head it would be prone to error.
Such is the inquisitiveness of child like minds .....
Alan