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Thread: Calibration performed for NTC probe w/ Phidgets

  1. #1
    Fusion Brain Creator
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    Calibration performed for NTC probe w/ Phidgets

    So, I calibrated a NTC probe:

    -- AVX Type NI24 --

    with a 463 ohm resistor, in a voltage divider arrangement.

    From 35 Degrees F to 190 Degrees F.

    I can say with 95% confidence that the following curve fit equation is accurate to +/- 1 degree from 35 degrees to 190. In some cases it is better than .3 degrees F accurate.


    N = -1.4618 * N ^ 6 + 21.062 * N ^ 5 - 127.38 * N ^ 4 + 409.96 * N ^ 3 - 731.9 * N ^ 2 + 626.52 * N + 10.658

    Where N is the phidgets sensor raw value.

    I've incorporated this logic into the latest revision of the RR source code.

    PM me if you need some of the thermisters, they're more accurate and cheaper than the phidgets variety.

    http://i2.ebayimg.com/04/i/06/ff/90/56_1.JPG

    Compare to Phidgets, which has an accuracy of +/- 4 degrees F, and are mounted on a board....these thermisters can be epoxied to anything.

  2. #2
    The Curator
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    Great work, good find.
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  3. #3
    The Last Good Gremlin GizmoQ's Avatar
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    Quote Originally Posted by greenman100 View Post
    From 35 Degrees F to 190 Degrees F..
    35???
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  4. #4
    Fusion Brain Creator
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    Quote Originally Posted by GizmoQ View Post
    35???
    yes, I calibrated them in a variable temperature water bath. Below 35 and I risked freezing, and I didn't seen a need to go above 190. They'll work below 35, just not be as accurate.

  5. #5
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    care to share the code ? If I can merge it the main sources, you won't have to add it when new releases come in. Just email it to me (my email is on my public profile).
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  6. #6
    Fusion Brain Creator
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    Quote Originally Posted by guino View Post
    care to share the code ? If I can merge it the main sources, you won't have to add it when new releases come in. Just email it to me (my email is on my public profile).
    by now, between this and the other thread, there is sooo much. I think I commented it all, but I'm not sure. I had to modify frmLoader, frmSkin, and modRoadRunner. Is that ok?

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