How to measure distance accurately
adam wrote 02/26/2015 at 22:56 • 1 pointAnyone have good ideas on how to measure linear distances (electronically) between 0" and 60" to an accuracy of 1/32" or 1/64"?
Anyone have good ideas on how to measure linear distances (electronically) between 0" and 60" to an accuracy of 1/32" or 1/64"?
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The tolerances for measuring this using direct light reflection are in the pico seconds (the speed of light over an inch very very fast), st device is quite impresive if it uses this, but it does explain the min 10cm distance it has.
Using a linear sensor/camera and angle of the reflected laser beam method is "simpler" but not sure about the accuracy and still requires trig and measuring position of the reflected dot on the linear sensor.
I suppose you've already discounted the simplest distance measurement which is a simple ultrasonic transponder, not sure of accuracy there.
Stick with the string pot or encoder if you can do it mechanically.
Good luck :-)
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There is a "Time of Flight" sensor that measures distance using light. It says that the range is 10cm, but it is possible to extend that range if a special reflector is used on the target. Look here for it:
http://www.st.com/web/en/catalog/mmc/FM132/CL2136/SC1934/PF260441?icmp=pf260441_bn_home_feb2015
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String potentiometers work fine, a very simple solution. You´ll just need an analog input on your MCU, no further components required.
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Thanks, guys!
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I would use a linear encoder. There are optical ones and magnetical ones. The specs on commercial ones are amazing. Some inkjet printers use a propriatary system that some have hacked. Ben Krasnow apparently has a post about these kind of things: http://benkrasnow.blogspot.nl/2010/02/linear-position-tracking-with.html
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Stanley makes (or made) a digital tape measure. It used a physical metal tape which had markings on the back which an optical sensor could read. It also had some sort absolute encoder inside with the tape reel. The device had an LCD where the distance could be read (it could also be read from the tape itself). The tape measure didn't have a data port on it but the PCB inside had an unpopulated header which included a serial output. By carefully drilling a hole through the case, I was able to solder wires to this header and read the output (which was ASCII characters). I thought it strange this serial port had no connection to the outside world.
I don't recall how long this tape measure was, but I think it was over 5'. I think it was accurate to 1/32".
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Electronically = some kind of signal that can be read by computer or microcontroller. Distance could be bridged mechanically or optically - sound probably not accurate enough.
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When you say "electronically" do you mean that nothing physical can bridge the distance?
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