## 3065Re: Tweaking options

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• Jul 1, 2006
hwy9,

The origin tweak is used when you have a situation where the sensor
is not reporting high enough when the humidity is high and now low
enough when the sensor is low. This happens to be a problem with the
La Crosse humidity sensors.

If you use a regular tweak as you mention, this will skew the higher
values more than the lower values. It will also either increase or
decrease the reading at higher and lower values depending on the
tweak value (1.20, increase by 20%, .80 decrease by 20%).

Lets say I am a CWOP member and compare my humidity to the analysis
humidity. The analysis curve has a high of 90 and a low of 20. My
curve follows the analysis curve but has a high of 80 and a low of 30.

When the analysis is humidity level is high, my readings are not high
enough, when it is low, mine are not low enough.

This method of tweaking assumes that there is some inherent 'mid-
point' where the sensor is accurate. It also assume that 'error' is
proportional whether above or below this origin.

Whether or not there proves to be an accurate midpoint is debatable.
This mid-point may move based upon different temperatures and
humidity levels. For the past several months, my tweak values have
worked well. Whether or not I will need to re-adjust those tweaks
this winter, that remains to be seen.

In my case, I have followed the analysis and it seems to be accurate
around 60%. That is the origin.

When a value is read, it is compared with the origin. If the reading

If it is above 60, the tweak value is multiplied with the deviation
from 60, then added to 60.

If the reading is below 60, the deviation from 60 is multipled by the
tweak and subtracted from the current reading.

When using the origin, keep in mind that the tweak value is applied
to the distance between the reading and the origin, not the reading
itself like a regular tweak.

In my case, I have a tweak value of 0.20 and an origin of 60.

So if the reading is 80%, after the tweak, it will be 84%.

New value = (80 - 60) * .2

If the reading is at 30%, after the tweak, it will be 24%.

New value = (60 - 30) * .2

Hopefully that clarified the meaning of the tweak for you.

If you have more questions, let me know.

--- In wuhu_software_group@yahoogroups.com, "hwy9_weather"
<akers305@...> wrote:
>
> Can you explain the Use Origin Of tweaking option? I understand the
> multiplier role in the simpler tweaking option, but I gather the
Use
> Origin of is designed to tweak more on the high end and less in the
> mid range. I am speaking mainly of the humidity sensor.