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

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.

On 29 Aug 2005 04:17:01 -0700, "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?

Gear tooth sensors are usually hall effect (magnetic). Sealed
optical encoders are used on rotating shafts too. Some lower-speed
machines use proximity switches, aka proxis or ECKO's (Eddy Current
Killed Oscillator) which are highly immune to both chips and dirt, but
are not as fast as Hall or optical.

"Industrial Machine" includes a huge variety of requirements and
environments. Which is the "right" sensor depends greatly on the
specific application.

"Dave" wrote in news:1125314221.369142.83390
@f14g2000cwb.googlegroups.com:

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


Depends on the application Dave. If you are sensing metal in close
proximity to the sensor, you will most likely be using a normal
capacitive / hall effect proximity sensor. These have a limited range,
depending on the barrel size. (See Balluff BES series - Balluff.com)
If you need to sense items farther than say 3-4 mm, there are several
options. There are retro-reflective, many with adjustable ranges, these
contain both the infared emitter and receiver in one body. There are two
types, one requires a reflector mounted some distance away, the other
type does not require a reflector. (See Balluff BOS series)
Then you have the fiber-optic beam sensors, in which you have separate
emitter/receiver, placed some distance apart. There is a light beam that
travels between them. (See Banner OSFX series )
Then you have the various laser sensors, these are programmable for
sensing distance (See Keyance corp)
You also have untrasonic type distance sensors (See Banner/Turck website)


--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

http://www.machines-cnc.net:81/

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.

On 29 Aug 2005 04:17:01 -0700, "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

Hall Effect sensors

Gunner

In article 1125314221.369142.83390
@f14g2000cwb.googlegroups.com, says...
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?


Optical sensors are widely used. Some are more susceptible
to dirt than others, particularly those that sense
reflected rather than transmittd light. Some good info from
Banner here...

http://www.bannerengineering.com/lit...resources/refe
rence/

Banner uses the term "excess gain" to indicate how
sensitive a given sensor is to dirt or other attenuation of
the light beam.

Photosensors of the sort Banner makes are relatively
expensive compared to inductive proximity sensors, which
have become a commodity item in the common configurations.
They're available for around $20.

Air cylinders can be ordered with magnetic pistons that
will trigger Hall effect or reed switches that clamp to the
cylinder.

And sometimes an old fashioned mechanical limit switch is
the best solution.

Ned Simmons

"Ned Simmons" wrote in message
...
In article 1125314221.369142.83390
@f14g2000cwb.googlegroups.com, says...
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?


Optical sensors are widely used. Some are more susceptible
to dirt than others, particularly those that sense
reflected rather than transmittd light. Some good info from
Banner here...

As Ned sed. But be cautious about one thing.

I design automation for pyrotechnic manufacturing. One design used dozens
of IR reflective sensors to pick up end-points on various parts. I had
debugged the firmware and tweaked the hardware in my shop before delivering
the unit. It worked nicely.

Imagine my consternation when the very first time we fired it up on site, it
crashed several actions.
Huh?

Well, it turned out the "IR" sensors were just as sensitive to visible light
as to IR. Ambient light (not direct sunlight) from a nearby window was
fooling all the sensors whose targets were illuminated by the window.

Several wasted hours of building guards and shuttering the windows solved
the problem -- but what a ****er!

LLoyd

In article ,
says...

"Ned Simmons" wrote in message
...
In article 1125314221.369142.83390
@f14g2000cwb.googlegroups.com, says...
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?


Optical sensors are widely used. Some are more susceptible
to dirt than others, particularly those that sense
reflected rather than transmittd light. Some good info from
Banner here...

As Ned sed. But be cautious about one thing.

I design automation for pyrotechnic manufacturing.

Yikes, hope your liability insurance is paid up g. My
agent got jumpy just beacause I mentioned that I
occasionally build automation for a medical products
manufacturer, I wouldn't dare mention explosives to him.

One design used dozens
of IR reflective sensors to pick up end-points on various parts. I had
debugged the firmware and tweaked the hardware in my shop before delivering
the unit. It worked nicely.

Imagine my consternation when the very first time we fired it up on site, it
crashed several actions.
Huh?

Well, it turned out the "IR" sensors were just as sensitive to visible light
as to IR. Ambient light (not direct sunlight) from a nearby window was
fooling all the sensors whose targets were illuminated by the window.

Several wasted hours of building guards and shuttering the windows solved
the problem -- but what a ****er!

If it was only several hours you got off easy g. I
remember running into this once or twice, but can't recall
the exact circumstances. Maybe on a machine with a UV lamp
for curing a potting compound? Most photosensors modulate
the light source and tune the detector to be sensitive to
its own source. This is done primarily to eliminate
crosstalk between sensors, but has the side benefit of
reducing sensitivity to ambient light.

Ned Simmons