I have two glass scales with quadrature outputs that are mechanically opposed on a milling machine. One is on the quill and the other is on the knee. Moving the quill down is mechanically the same as moving the knee up and vice versa.
What I would like to do is to "sum" their outputs such that if I moved the quill down by 0.1" and left the knee alone, the DRO position reading would be reduced by 0.1". However if I moved the quill down by 0.1" AND the knee down by 0.1", the DRO position would remain unchanged. Conversely, if I moved the quill down by 0.1" and the knee up by 0.1" the DRO position would be reduced by 0.2".
Both scales are from the same manufacturer and have single ended quadrature outputs. Can I accomplish what I want by simply connect the respective phases together in parallel and feeding the combined signal to the DRO? When I say "respective" phases I realize that could be A-A and B-B or A-B and B-A depending on the scale orientation. Will I need some sort of buffer circuit to combine the scale outputs, or do I have to dump in a microprocessor to create a position counter for each scale and combine the positions and then generate a new combined quadrature output?