Re: [CAD_CAM_EDM_DRO] Inductive vs capacitive proximity sensors?

Peter
I cannot give you a definitive answer because different sensors probably
operate differently to the ones I have tested. However in the course of
characterising our inductive transmission system we found a lump of metal
in front of the transmitter coil was a very effective check on the basic
operation of the transmitter. It did not matter what metal was used, ally
was just as good as steel. Coins will work well, even thin foil.

The way I look at it is the sensor is a tuned system. When no metal is near
it oscillates at its natural frequency and consumes little power. When you
bring a piece of metal near the tuning is modified and the power to the
coil changes. The change in power is used to trigger the output. At the
high frequencies we use almost any metal will do, although the sensing
range will vary slighlty.

At work we use cosmetically imperfect transmission units as inductive
proximity sensors in our machine shop. They sense the position of carousels
holding raw materials and tools. If swarf build up is likely a coolant or
air jet may be required to clear the working face before use!

Regards
Bill Phillips

> I know this subject is on the fringe of our group topic. Does anybody have
>any experience with proximity sensors? I have a part I want to sense in the
>collet before the cnc closes the collet. I don't want to machine air or snap
>the collet. The part in question is a hand inserted but later possibly robot
>inserted aluminum blank. I understand ferrous parts are easy with inductive
>sensors. Do aluminum parts trigger inductive sensors? Any body play with
>capacitive sensors? Are they as a group sensitive to soluble oil? mineral oil
>based coolant?
>
>Any comments are appreciated. I've not played with these things before.
>
>Peter
>THRD, Inc.