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Can anyone point me towards whats best for relatively low cost distance measuring in the 0-36" range (or 0 - 1m range) with 1/16"/1mm accuracy. My initial approach was going to be to hack a laser tape measure, but wanted to know if that was the best in cost vs accuracy.

Essentially looking to measure how close I am to a stationary metal plate.

Thanks for any help.

  • Most "laser" tape measures are merely a laser pointer strapped to an ultrasound range finder. Ultrasound is by far the simplest and cheapest option though its accuracy can sometimes be a little "iffy". – Majenko Jun 22 '16 at 14:27
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    Your suggestion regarding "most" is an invalid generalization and inaccurate as well. Laser rangefinders use lasers, ultrasonic rangefinders use ultrasound, with perhaps a laser indicator for aiming, but it is necessary only to read the product specifications to determine the method of use. – fred_dot_u Jun 22 '16 at 15:03
  • @fred_dot_u If a "laser tape measure" is cheap enough to be destined for hacking then it's using ultrasound. All the "laser tape measures" I have ever seen at DIY stores, or have ever owned, or have ever used, have been ultrasound. Yes, there are laser based range finders, but they are considerably more expensive and outside the "hackable" price bracket. – Majenko Jun 22 '16 at 15:23
  • dx.com/p/… Granted, it's out of stock, but fifty-one american dollars is low enough cost to be hacked and it's laser. Fully optical, zero ultrasound. My point was that "most" are not. Some are laser, some are ultrasound. You've added an interesting ambiguity to the equation as well. "Cheap enough" is difficult to pin down. Fifty or one hundred dollars is cheap enough if someone has enough motivation and can make a project work. Two hundred dollars is cheap enough if success is a certainty. All this is opinion, of course. – fred_dot_u Jun 22 '16 at 16:39
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You will likely find the best accuracy is derived from a laser-based measurement. My Bosch is laser only, no ultrasound component and has 1/16" resolution. For your application, the six inch minimum distance limitation of the Bosch is outside your specifications.

Because laser measurement devices use time versus distance, it's possible you could construct a mirror chamber with front-surface mirrors that would cause the laser to travel six inches before exiting the chamber, overcoming that limitation. The calibration should be straight-forward, as you'd place the chamber flush and adjust your mirror placement until you read the exact expected compensation distance.

You would need only small mirror panes, which would not "break the bank," but if you find a discarded large-screen projection television, the mirror within is front surface and quite large. Front surface mirrors should not have contamination from touching and should be cleaned with care, as you can erode or otherwise degrade the reflective surface.

I found this site: http://blog.qartis.com/arduino-laser-distance-meter/ which looks promising for a different model of laser rangefinder, although the creator has run into a stumbling block or two.

It would appear that the key is to overcome the minimum distance limitation, perhaps as I suggested above, and interfacing with serial communications of the arduino.

One of the links I pursued involved the creator contacting the technical support of the manufacturer. The support ticket was closed as "resolved," in the manner of advising the user that the warranty was void by opening the case. Yeah, like that matters to makers and hackers!

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  • Thank you very much for this. I really like the idea of overcoming the limitation by using a mirror chamber. I wonder why most manufacturer's do not. – Rich Dominelli Jun 23 '16 at 12:09
  • Consider how much labor you might put into building a mirror chamber, as well as the effort in calibrating/tuning the light path. A manufacturer may not be able to design and build something that works for Joe Consumer, but we maker-folk are pretty resourceful. What cost is your labor when you are creating? For some of the stuff I build, for the fun and experience, it appears that I'm paying people to do this kind of work. But then again, what price is fun? – fred_dot_u Jun 23 '16 at 17:13
  • If you have a 3d printer or access to one, you could design a mirror chamber in which to glue or slide the mirror segments as well as include a compartment for the Arduino, although the image in my alleged mind may not match yours, as I do not know the precise application. – fred_dot_u Jun 23 '16 at 17:14

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