Hi MXJ,
I am sorry to see this 8 days after the posting, I didn't get an email for some reason.
Anyway, at the time of writing here, I also contacted CS Labs and they suggested something very simple. In order to feel safe for the CSMIO controller, they suggested that I use a separate 24VDC power supply, only for the auto touch plate. Baring in mind the input needs milliampers to get ON, the smallest 24VDC capacity will make it for you. I intended to buy a 0.42 A from Mean Well but ended with a 1A only because the first was not available locally and I didn't want to wait. Of course, the bigger the power supply, the bigger the current consumption. It is your choice.
Basically, I have a big clamp-like wire, which is preloaded with 0V from the separate power supply. When I am about to perform auto tool zero, I attach the clamp to the tool bit. The touch plate has a big (4 mm ^ 2 wire) soldered to it. The other end goes directly to the negative(-) of the CSMIO input used for auto tool zero. The (+) of the same input number is wired to 24VDC again from the separate power supply.
I feel that I need to mention I didn't go for two different touch plates. I only have one which can get to every part of the work table of my machine. For now, I haven't implemented the auto tool measurement because it is not necessary for the way I work.
When the tool touches the plate, the 0V goes through the touch plate to the CSMIO input and closes the loop which stops the feeding. I've measured my plate's thickness with a micrometer and have inserted a special line in the CS Labs's VB script to set Mach3's Z coordinate to that thickness.
I had some hard time finding the image I got from them in my CS Labs folder. Never mind, I found it in my inbox. If you have any questions on this, I will be glad to help.