If you need more than the 4 inputs on the TouchDRO adapter, you can also use a
summing interface. It combines 2 quadrature scales into one output.
On both of my mills, I use the W axis as an angular input for my rotary table. Which is easy on the mini mill, as there's only 3 scales, and no quill. My universal mill has 4 scales: knee, table, saddle, and ram. The saddle and ram are summed, but that would take up all 4 TouchDRO inputs, and leave no place to plug in my rotary table. The summing interface solved this.
The CPI for the ram and saddle scales was slightly different, so I averaged them... This does makes the Y-axis (or Z-axis, depending on if the head is horizontal or vertical) readout slightly off, but since I use 1um scales, the error is only a couple of tenths over the entire travel of both.