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Parallax Laser Range Finder - Do they need to calibrated out of the box? — Parallax Forums

Parallax Laser Range Finder - Do they need to calibrated out of the box?

Don MDon M Posts: 1,652
in Accessories
I just received 2 new range finders. The one designed by Joe Grand. It reports as version 2.0. Do they need to be calibrated out of the box? The reason I ask is it measures about 2" short on a 32" distance.

Thanks.

Comments

  • PublisonPublison Posts: 12,366
    edited 2016-08-11 15:55
    Version 2.0 is the latest. You still need to calibrate per the manual:
    X: Calibrate camera system for range finding
    To account for manufacturing and assembly variances, particularly related to the camera and laser diode
    alignments, each LRF Module must be calibrated. This occurs during production, but the LRF can be recalibrated
    by the user at a later date if desired. If a new major version of firmware is loaded (for
    example, upgrading from firmware version 1.0 to 2.0), the LRF will need to be re-calibrated.
    https://www.parallax.com/sites/default/files/downloads/28044-Laser-Range-Finder-Guide-v2.0.pdf
  • Duane DegnDuane Degn Posts: 10,588
    edited 2016-08-11 15:58
    I'm can't remember if there's a calibration procedure for the Joe Grand LRF. I think there's a list of constant one can change but I'm not sure about this. (Edit: It looks like Publison had the required information.) I'm pretty sure it's not supposed to need to be calibrated.

    How are you displaying the distance? Is it to the nearest inch or tenth of an inch?

    2" off at 32" is a 6.25% error and the specs claim less than 5% error. Have you tried reading in millimeters?

    Here's a video I made comparing the SF02/F with the Joe Grand LRF. My LRF was off about 4cm at an 86cm distance.



    Edit: The embedded player isn't working for me right now. Here's a link to the video.
  • PublisonPublison Posts: 12,366
    edited 2016-08-11 16:31
    Duane Degn wrote: »
    I'm can't remember if there's a calibration procedure for the Joe Grand LRF. I think there's a list of constant one can change but I'm not sure about this. (Edit: It looks like Publison had the required information.) I'm pretty sure it's not supposed to need to be calibrated.

    I guess it wouldn't hurt. I don't own one. (Note to Ken. Send me one). :)

  • Don MDon M Posts: 1,652
    Right now I'm using the demo software. It displays in tenths of an inch.
  • Don MDon M Posts: 1,652
    I set up the calibration distances of 20cm to 70cm and here are the results:

    20cm - 19.4 to (19.5) 2.5%
    30cm - 29.4 to (29.5) 1.7%
    40cm - (38.9) 2.75%
    50cm - (47.9) to 48.3 4.2%
    60cm - (56.9) to 57.5 5.2%
    70cm - 64.9 to (65.7) to 66.5 6.1%

    The numbers in the parenthesis are the numbers that come up most often. The other numbers would show occasionally. I also tried the "E" function to adjust the camera to the ambient lighting. Same results.

    Next I'll try calibration and see what the results are. Stay tuned.
  • Don MDon M Posts: 1,652
    After calibration things improved quite a bit:

    20cm - 19.6 2%
    30cm - 30.1 1%
    40cm - 40.4 1%
    50cm - 50.0 0%
    60cm - 59.1 1.5%
    70cm - 68.6 2%

    I seemed to get much more consistent readings also. I'm going to try and fudge the calibration on the longer distance to see if I can get it any closer.
  • Don MDon M Posts: 1,652
    I fudged the 2 longer distances and was able to bring them in closer to actual. Seems a lot better now.
  • Duane DegnDuane Degn Posts: 10,588
    Thanks for sharing your results Don.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    I am looking further into this. The modules should only need to be calibrated by the end user if you're the one who upgraded the firmware. Out of the box it should work just fine.
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