TempMult2 in cumulus.ini
Posted: 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?
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?
