Long Range Motion Sensor / Zero Speed

[RCoulombe]

In processing a moving forward hot metal bar (roughly heated at 2000F), I need to identify whether that bar is moving or not. We are currently having a sprocket rolling on the bar, reading the teeth with a solid-state proxy switch. Heat build-up becomes quickly an issue, both for the sensor and mechanicaly.

I am aware that non-contact motion sensors are available, but the detection range is so short (1.5" at most) that I would burn it almost instantly.

I either need a zero speed detector or simply a input, when the bar is moving, that I would treat with my PLC.

Would anyone know of any technology that could enable me to detect that the bar is moving without being to close to it - 24" is safe from radient heat.
Thank you,

 

[Skogsgurra]

Hello,

I think that this is the wrong forum. There is also the "Measurement & control instrumentation engineering" forum, which I think is better for your question.

Have you tried ultrasonic?

Gunnar Englund

http://www.gke.org

 

[itsmoked]

I would guess a laser range finder working through a band pass filter would work great!.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[ScottyUK]

Or microwave / radar. How do laser sensors behave when the target is a glowing billet of metal? Does the emitted light from the metal cause any problems for the receiver, or does the modulation take care of that?


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I don't suffer from insanity. I enjoy it...

 

[itsmoked]

You can use modulation. Generally though the laser is far, far, farrrrr brighter than the metal and so a bandpass filter that dumps most of the fairly uniform spectral light off the metal will leave the laser light obvious to a sensor. Microwave/radar would work too but you'd want to wave guide in and out of the area to get the e-tronics out of the hot zone.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[ScottyUK]

Ahh, an optical bandpass filter. I sse what you are getting at.

I don't think the spread from microwave or radar will be too bad at 24", although it depends on how big the billet is. I'm kinda envisaging a steelmill application, but the OP could do us a favour and define some more parameters, e.g. target size, atmospheric conditions, speed of movement, etc.


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I don't suffer from insanity. I enjoy it...

 

[itsmoked]

True! And I don't really see how 24" is going to be; "safe from radient heat".

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[machmech]

Hello

Forgive me I don't have a clue, what about radar? Would that be practical? Just thought!

http://www.getradar.com/

Chuck

A government which robs Peter to pay Paul
can always depend on the support of Paul.
- George Bernard Shaw

 

[itsmoked]

machmech; Yes radar would work well. You would use it strictly in Doppler mode which doesn't provide distance information but instead speed which is what the OP wants - confirmation of movement. It sends out a fixed frequency and then you monitor the reflected signal as being a different frequency from the original which occurs if motion is present. Same as a radar gun.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[nbucska]

Is the bar moved by rollers or are is it moving on rollers?

What is the range of the motion and of the speed?
How much accuracy do you need ?

What is the size? Any other data you can supply?



Plesae read FAQ240-1032
My WEB: <

http://geocities.com/nbucska/>

 

[SensorGooRoo]

There are good time of flight sensors that can detect up to 50m at 1.5mm of resolution and 10mm of linearity - thus getting away from the heat. if you have to have that close proximity there are special optical triangulation sensors fitted with special housings that can read .05 - 1mm in resolution and 1mm in linearity. These system cost between 2-7k and work very well. The heat will not be good for some IR and ultrasonic.

try globalspec for data on these kinds of sensors or

http://www.inrpoxsensors.com

 

[ScottyUK]

Optics and steelmills is a lousy mix for longevity. If you've ever been in one you'll have seen the mill scale, coke dust, and other every kind of airborne crud imaginable lying inches deep on every surface. It might help if a bleed of plant air was available to keep dirt from settling on the sensor optics.


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Sometimes I only open my mouth to swap feet...

 

[afterhrs]

You might want to check out the new Keyence PX-series infa-red optical sensors. If memory serves, they claim to have one that can read up to 40 M',they are dirt resistant and IP-67 rated. The one I had demonstrated can see thru your finger.

Keyence is not cheap, but they do make some nifty devices for problematic applications.

Best regards,
Afterhrs

 

[itsmoked]

afterhrs;
1) Keyence is cheap that is their forte!

2) The OP is talking about something as bright as the sun with respect to infa-red.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com