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I need some guidance on a project I am attempting. My hope is, someone on this forum has already tried this. I am looking to measure a linear movement (very slowly). I have seen some projects including digital caliper readouts, I am looking for something that uses sensors, so read out the sensor, not a caliper hack.

I have heard of hall sensors being used for this, encoders with stripes and such. So my question is, has anyone ever done a linear measurement with an accuracy of about 0.01mm (0.00039 inches). If so, could that someone point me in the right direction (type of sensor best for the job).

Thanks.  smiley-mr-green
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How much $$$ you have to spend, and under what conditions do the measurements need to be made? 
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Is there a way to (mechanically optically or otherwise) "zoom" the distance?
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No way to zoom in, good suggestion though. I am not on a tight budget for this project $200 is not a problem for this one. The conditions are clean, no need for error corrections or anything like that.
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I need some guidance on a project I am attempting. My hope is, someone on this forum has already tried this. I am looking to measure a linear movement (very slowly). I have seen some projects including digital caliper readouts, I am looking for something that uses sensors, so read out the sensor, not a caliper hack.

I have heard of hall sensors being used for this, encoders with stripes and such. So my question is, has anyone ever done a linear measurement with an accuracy of about 0.01mm (0.00039 inches). If so, could that someone point me in the right direction (type of sensor best for the job).

Thanks.  smiley-mr-green

So...10 micrometers? A human hair maxes out around 170 micrometers.

I'd say yes, you CAN do it. But, it won't be with anything from Sparkfun.

Maybe if you used some kind of ridiculously high gear ratio to translate it into something larger first?

What are you measuring? Why?
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You can use a laser beam and count how many times the intensity increases and decreases during the motion. A laser is made into two beams using a prism and mirrors. The two beams hit a phototransistor. One beam is the reference beam and it does not move. The second beam hits the target surface and reflects back to the detector. The phototransistor will respond to constructive interference and destructive interference by giving an output current that is an analog of the number of wavelengths that the target has moved.

Example :  IR laser beam infra red with a wavelength of 1um = .001mm
The target moves .1mm and the phototransistor current increases and decreases 100 times as 100 wavelengths are measured.  When the reference beam has a positive phase and the target beam has a positive phase, the current is high. When the reference beams has a positive phase and the target beam has the opposite phase, the current is low.

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No way to zoom in, good suggestion though. I am not on a tight budget for this project $200 is not a problem for this one. The conditions are clean, no need for error corrections or anything like that.

I'm thinking you might need to add a few more zeros to that for this level of accuracy. Quite a few materials expand more than 0.01mm when the temperature changes.
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That seems to be the general consensus. I decided to go with the caliper option anyway, its not a neat option but it will do the trick. I'm going to measure camshafts -> valvelift. So linear measurement of the valvelift vs rotation of the camshaft in degrees.

Thanks for all the tips and advice, will post some more when I reach a solution.

For anyone interested:
http://nut-bolt.nl/2012/reading-digital-calipers-with-an-arduino/

Or:
http://www.instructables.com/id/Reading-Digital-Callipers-with-an-Arduino-USB/#step1
« Last Edit: July 03, 2013, 04:54:18 pm by blipinthedata » Logged

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I am not on a tight budget for this project $200 is not a problem for this one

I'm going to measure camshafts -> valvelift

It seems a bit strange that you are ruling out mechanical amplification, then, because it would have to be a pretty strange setup where that wasn't possible.

You're also asking for massively better resolution than would normally be required to measure valve lift, too. The valve clearance in a running engine goes all over the place and also varies with wear and so on. Do you actually need the resolution down to a fraction of a thou?

Having said all that, you could probably find a digital dial gauge around the sort of budget you're quoting and that would get you far better resolution than you're asking for.
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What about the digital gauge on this page http://www.arceurotrade.co.uk/Catalogue/Measurement/Dial-Gauges

...R
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A fixed magnet and a magnetic sensor?
although a magnetic field changes depends on angle and possible distortions (it is complex - http://en.wikipedia.org/wiki/Magnet -) it might be reproducible in your configuration
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