How do I connect a Z-Axis touch plate to the Planet-CNC USB interface?

Semi automatic measuring is possible. 1. Place movable tool sensor (touch plate) on material. 2. Click "Measure Offset Z". Tool will move down, touch sensor and move up. 3. "Measure Offset Z" button is still down. 4. Click "Offset - Current Z" - this will set offset Z 5. Click "Measure Offset Z" again to release it and restore normal mode." The connections to the USB interface is as follows: - The spindle is connected to the gnd terminal (which is also connected to the end mill). Alternatively, you can connect the gnd directly to the end mill is access is permitted. - The touch plate (movable tool sensor) is connected to the Z-- terminal. What will happen: When the end mill (gnd) is in contact with the touch plate (Z--), there will be a connection from gnd to the Z-- triggering this Z-- action and the software will recognize the connection (like a button press, or a limit switch triggering). Additional Information: Additional Information: