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TempMult2 in cumulus.ini

Topics about the Beta trials up to Build 3043, the last build by Cumulus's founder Steve Loft. It was by this time way out of Beta but Steve wanted to keep it that way until he made a decision on his and Cumulus's future.

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Adrian Hudson
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TempMult2 in cumulus.ini

Post by Adrian Hudson »

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 »

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: 219
Joined: Mon 03 Jan 2011 4:27 pm
Weather Station: Davis Vantage Pro2
Operating System: Win 7
Location: Willand, mid Devon.
Contact:

Re: TempMult2 in cumulus.ini

Post by Adrian Hudson »

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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