One well-known brand of DRO uses magnetic sensors - Sony.

Bob Swinney
"Don Stauffer" wrote in message
...
Dave wrote:
Are optical interrupters used in industrial machines or are they too
vulnerable to dirt? I'm guessing magnetic sensors might be more immune
except that the magnets might attract ferrous grit. What is the
preferred proximity/shaft sensor?

Thanks

People I worked with at one time were more concerned with the grease, oil,
and dirt than with ferrous chips, so they tended to use magnetic sensors
more. The optical can be more precise, but indeed are subject to
obscuration. The applications we were dealing with was on engines (autos,
trucks), but I got the feeling the same was true for general machinery.
One had to be careful to enclose optical sensors if dirt and grease were a
concern.