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'[EE:] brainstorming request: measuring small dista'
2003\12\03@075102 by Vasile Surducan

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Hi there,

The problem which requires to be solved its a small distance measurement
at high speed (about 15cm/second) in a high EM radiation environement
(near a few KW generated from 300KHz inductors). The medium distance to be
measured is about 2mm, between a a metal surface which have inflexions
(it's not a plane surface) and a moving tool. The metal surface is painted,
dirty and gruffly, where the paint+dirt have a variable thickness.
The generators can't be shutted off while the measurement is performed.
I will be glad to hear any possible ideea from specialists (or just
thinkers) from these lists.

thank you in advance,

Vasile
http://surducan.netfirms.com

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2003\12\03@075726 by Mike Harrison

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On Wed, 3 Dec 2003 16:09:36 +0200, you wrote:

>Hi there,
>
>The problem which requires to be solved its a small distance measurement
>at high speed (about 15cm/second) in a high EM radiation environement
>(near a few KW generated from 300KHz inductors). The medium distance to be
>measured is about 2mm, between a a metal surface which have inflexions
>(it's not a plane surface) and a moving tool. The metal surface is painted,
>dirty and gruffly, where the paint+dirt have a variable thickness.
>The generators can't be shutted off while the measurement is performed.
>I will be glad to hear any possible ideea from specialists (or just
>thinkers) from these lists.
>
>thank you in advance,
>
>Vasile
>http://surducan.netfirms.com

What resolution/range do you need ?
Do you want to measure the distance to the paint/dirt, or to the metal surface regardless of
contamination ?

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2003\12\03@080348 by Vasile Surducan

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On Wed, 3 Dec 2003, Mike Harrison wrote:

{Quote hidden}

 10% to 20% will be ok

> Do you want to measure the distance to the paint/dirt, or to the metal surface regardless of
> contamination ?

 distance to the metal surface

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2003\12\03@081221 by Olin Lathrop

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Vasile Surducan wrote:
> The problem which requires to be solved its a small distance
> measurement at high speed (about 15cm/second) in a high EM radiation
> environement (near a few KW generated from 300KHz inductors). The
> medium distance to be measured is about 2mm, between a a metal
> surface which have inflexions (it's not a plane surface) and a moving
> tool. The metal surface is painted, dirty and gruffly, where the
> paint+dirt have a variable thickness.
> The generators can't be shutted off while the measurement is
> performed.
> I will be glad to hear any possible ideea from specialists (or just
> thinkers) from these lists.

How about shining a thin light beam at an angle and using parallax from
another sensor to measure distance?

Are mechanical means out of the question, like an idler wheel on a spring
loaded lever, then measure the deflection of the lever?


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

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2003\12\03@082506 by Mauricio Jancic

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Cant you make a small line with an abrasive tool on the metal and use a
reflective measurement system?, or perhaps add a small mirror to the
painted surface?

Mauricio D. Jancic

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2003\12\03@094042 by cisco J. A. Ares

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Olin Lathrop wrote:

{Quote hidden}

At Edmund Scientific (somewhat expensive, but they have a bit of
everything) they have laser beams and special heads that split the light
spot into a line. You can put a camera in front of the tool, and the
laser at, say, 45 degrees, but with the light line aligned along the
tool. The image is going to be a vertical line while the laser is on the
tool and a diagonal line when the laser shines on the surface of the
metal. The pixel of this line that is aligned to the first segment (from
the tool) is right beneath the tool, so the distance can be calibrated
and then measured.

According to the camera lenses, this measurement can be made through a
relatively long distance, trying to avoid all that EM fields, or at
least you can build an enclosure for the camera.

The camera resolution and the thickness of the laser line will give you
the accuracy of the system. You will need fast electronic shutter,
though, and a good quality frame grabber

Hope this helps
Francisco

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2003\12\03@100815 by Madhu Annapragada

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If you are looking for an "industrial automation application" solution as
opposed to a one-off hobby type application, look up Keyence sensors
(http://www.keyence.com); they have a couple of laser based sensors and a few small
range proximity sensors that do this sort of thing.
Madhu

>{Original Message removed}

2003\12\03@111128 by Brian Clewer

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Re posted with the correct TAG!  Sorry

On 03 December 2003 15:02 Madhu Annapragada wrote:

> -----Original Message-----
> If you are looking for an "industrial automation application"
solution as
> opposed to a one-off hobby type application, look up Keyence sensors
> (http://www.keyence.com); they have a couple of laser based sensors and
> a few small
> range proximity sensors that do this sort of thing.
> Madhu


The problem with light based sensors is that the metal beam is
covered with a variable thickness of paint and grime.  The laser
/ light sensor would only pick up the surface of the beam and not
the metal below that.

Brian.

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2003\12\03@120627 by Madhu Annapragada

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I know for a fact that Banner and Turk both make Inductive proximity sensors
that can be used in harsh environments (both mechanical and electrical). Now
the problem is that these sensors would give you a yes or no answer to the
presence of metal very accurately but how are you going to measure distance
from that? Fixed distance sensing is one thing but if you want to sense
metal that can vary in distance from the sensor, you will need an analog
output that is fairly linear in your measurement range; you might try
talking to applications engineers at Turk, Keyence and Banner. Between them
I am sure they will recommend a good solution albeit an expensive one.
Madhu

>{Original Message removed}

2003\12\03@123832 by Simon Davies

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How about the versions of digital vernier callipers that are intended for
use on industrial lathes and milling machines. Most of these have a serial
output and can be connected to a dedicated display or to your own display
device.
They are intended to survive harsh environments and could be hooked up to
constantly touch your beam or be spring loaded against it. They come in
various lengths from 200mm/8inches up to 1m/39inches or so and I am sure
longer ones could be obtained.
Alternatively try a digital DTI (dial test indicator) which has a throw of
about 25mm/1inch and a display and (on mine) a serial output and a ball
bearing on the end of a plunger allowing contact.

Hope this helps,

Simon

-----Original Message-----
From: Madhu Annapragada [spam_OUTmaprTakeThisOuTspamCOMCAST.NET]
Sent: Wednesday, December 03, 2003 6:05 PM
To: .....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU
Subject: Re: [EE:] brainstorming request: measuring small distance in
harsh environment

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2003\12\03@135634 by DOC

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At 08:10 AM 12/3/2003 -0500, you wrote:
>Vasile Surducan wrote:
> > The problem which requires to be solved its a small distance
> > measurement at high speed (about 15cm/second) in a high EM radiation
> > environement (near a few KW generated from 300KHz inductors). The
> > medium distance to be measured is about 2mm, between a a metal
> > surface which have inflexions (it's not a plane surface) and a moving
> > tool. The metal surface is painted, dirty and gruffly, where the
> > paint+dirt have a variable thickness.
> > The generators can't be shutted off while the measurement is
> > performed.
> > I will be glad to hear any possible ideea from specialists (or just
> > thinkers) from these lists.
>
>How about shining a thin light beam at an angle and using parallax from
>another sensor to measure distance?


This should work especially if you use a laser.

If you're looking for defects or flaws, you might also want to digitize the
sensor information and run it thought a trained neural network.


>Are mechanical means out of the question, like an idler wheel on a spring
>loaded lever, then measure the deflection of the lever?


I'd be surprised if a mechanical solution would be sensitive or fast
enough.

DOC



http://www.robot-one.ca

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2003\12\03@141052 by DOC

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Or something like an ultrasonic distance sensor.

Here's one supplier:
http://www.senix.com/

DOC



At 12:04 PM 12/3/2003 -0500, you wrote:
{Quote hidden}

http://www.robot-one.ca

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2003\12\03@170836 by Russell McMahon

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> The problem which requires to be solved its a small distance measurement
> at high speed (about 15cm/second) in a high EM radiation environement
> (near a few KW generated from 300KHz inductors).

Thinker only :-) :  Capacitance sounds like a good starting point.
If you use an excitation frequency which is not harmonically related to the
other major signals present then filtering may be enough to remove unwanted
signals.

       RM

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2003\12\04@120315 by Peter L. Peres

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You can resort to pneumatics. A pneumatic proximity sensor is non-contact,
keeps itself clean at all times, and is imprevious to any EM field (the
pressure gauge is mounted remotely with the regulator). You will not have
trouble finding compressed air at 0.2-1l/sec at an installation with
'several KW' in it.

Peter

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