digitizing probe

Gentlemen,

I am not trying to get things going on the digitizing thread again, but I have a question for you electronics geniuses ( I say that respectfully, and gratefully):

I am using a digitizing probe made by Fowler. It is a copy of a Renishaw cmm probe that the patents have now run out on. It has no debounce electronics or anything like that, just a set of contacts configured as the Renishaw probes are. My question is:

I am applying + 12 volts through the probe contacts then through a 100 kohm resistor then to ground to protect the contacts from too much arcing. Should I put a capacitor accross the contacts to further protect them from arcing? It seems as though a .1 ceramic might help.


By the way, I am using 12 volts, because when I tried to use 5 volts, the contact resistance sometimes gave me erroneous indications. I compare the signal coming from the probe to a reference of 8 volts using an LM339 to avoid erroneous indications produced by contact resistance. I also use software to debounce the contacts.

Thanks again for your help.

Tom Eldredge


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