I am needing some help!
I have been upgrading an older CNC plasma table, using DMMTech DYN4 servo drives and matching AC servo motors,
For the Initial torch height sensing or material height sensing i guess, i was hoping to use the same approach as the original setup,
this was Ohmic sensing plus using the current monitoring output of the drives, the voltage output would feed an Arduino with a small program to switch an output above a certain threshold.
Unfortunately this isnt going to work with the output from the drive, as they have a range of +-10amps, the drive is 3.5A max, and i doubt i would see anywhere near that even!
What that means is the range of voltages output from the drives current monitor is only a few millivolts.

I had wondered if something like this on just one phase of the motor would work;

https://www.amazon.co.uk/AZDelivery-...6&sr=8-10&th=1

But im not sure if that would be any better! also this was one of the reviews;

" These worked perfectly, and I guess you could call them a success on their own terms. But sadly they aren’t as useful as you might think; this is no fault of the design or manufacture, just intrinsic to the way they work. They’re very sensitive to electrical noise and don’t seem to have very fast response. They have some advantages over simpler solutions such as the fact you can connect them at the positive or negative end of whatever you’re trying to measure, and also they have a very small impedance.

I was trying to use one to measure the current used by a servo motor, but in the end abandoned it and just stuck a 0.1 ohm resistor in series with the servo and measured the voltage across it. Not as elegant but simpler and more effective."


So other than having to convert my torch holder to a floating head design! Is there any ideas on how i can implement the current monitoring idea?
Plasma torch contacts plate, servo has to output more current to keep moving, above certain threshold triggers the "probe" input in mach 3

any suggestions gratefully received!!
cheers
sorry for the boring post!