A while back I wanted to upgrade my 3d printer to hall effect sensors. When I found out each sensor was going to cost me around ~$20USD per unit and I needed at least 3 of them I dropped the idea. After some digging I found out about the A3144 sensors and their cost being less than .20 cents per unit from this individual NotANumber and telling me the cost was less than 20 cents per unit I figured I had nearly nothing to loose.
The original writer of the article above does a good job mostly but fails to provide a diagram. A quick google search and I found what I needed.
These end stops seem to be accurate to less than .0005inch or less than .01mm is all my gauge can measure. Overall I am very happy with the performance. As a side note being that these are much more accurate it has allowed me to level my 3d printer bed with a .03mm feeler gauge. Overall I am very happy with their performance. I will be using these in future builds as well. (Thinking about a small CNC mill.)