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    TempMult2 in cumulus.ini

    Discussion of version 3 of Cumulus, which runs on Windows, Linux, and OS X. All Cumulus MX queries in here, please.

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    Adrian Hudson
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    TempMult2 in cumulus.ini

    Post by Adrian Hudson » Sat 22 Oct 2016 7:57 pm

    Steve,

    Some time ago, at my suggestion, you added the TempMult2 paramer in the Offsets section of cumulus.ini to allow correction of non-linear errors in the temperature sensor. I used this facility until my sensor failed and on replacing it I found the new one to be so accurate that I no longer really needed any correction other than a slight offset - no multipliers.

    I have replaced the sensor again (it didn't fail, I just wanted a faster acting one) but this one does need use of both multipliers as it has a definite curve to its errors.

    The problem is, I can't remember how to convert the figures in the error equation into entries for the .ini file.

    The error = (-0.0010460315 * temperature ^ 2) + 0.0024900526 * temperature + 0.1810093206

    This result, being the error in the temperature, needs to be subtracted from the temperature to get the corrected temperature.

    The documentation says that TempMult2 is: " "Second order" multiplier by which measured outdoor Temperature is to be corrected, this means that the logged reading can be (TempMult2 * measured-temp * measured_temp) + (TempMult * measured_temp) + TempOffset"

    But it appears that you CAN'T just plug those figures in to the three ini entries like this:
    TempOffset = 0.1810093206
    TempMult = 0.0024900526
    TempMult2 = -0.0010460315

    ...if you do, you get tiny output figures. The documentation says you can, but it appears to be wrong - or I am misunderstanding it.

    How do I convert the error figures into ones that I can plug into the ini?

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    steve
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    Re: TempMult2 in cumulus.ini

    Post by steve » Sat 22 Oct 2016 8:49 pm

    I added TempMult2 to Cumulus 1; I haven't yet added it to MX. I'll do that in the next build.
    Steve

    Adrian Hudson
    Posts: 216
    Joined: Mon 03 Jan 2011 4:27 pm
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    Re: TempMult2 in cumulus.ini

    Post by Adrian Hudson » Sat 22 Oct 2016 9:12 pm

    ahhhhhhhh! That explains a lot! I couldn't figure out what I was doing wrong!! Thanks Steve, I look forward to the next build :-)

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