Re: Analog Opto Isolator?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "vrsculptor" <vrsculptor@...>
wrote:

>
> Graham,
> The zener with a resistor would work but I get no isolation. I would
> have to tie the micro ground to the EDM ground which would be seeing
> all kinds of RF from arcing. Peter Homann's suggestion of a digispeed
> with a zener to protect it should work. I was hoping for something
> simpler.
>

RF on the ground with respect to what? The ground can go up and down
as it pleases with respect to earth say but your micro would just ride
on top of it.

If you really want to keep things separate and I can see why you might
then just use a comparator (or several) to detect the threshold(s)
voltage and allow that to drive an opto-isolator. If you want to be
able to set the voltage via software then you could use a serial ADC
also driving an opto.

Another way to get an isolated reading is to measure gap current
instead of voltage and you can use a LEM module for that (hall based
current sensor made by Lem and others). Actually a neat way to do it
especially if you fancy any micro EDM as it does not add gap capacitance.

Graham