Callibrating Humidty

[ironeagleuk]

If I adjust my humidity by -6, will it ever get up to 99%?

[steve]

No, the highest it could reach is 93 or 94.

[nking]

Hi Steve,

So I guess the reverse is true but does your code stop reporting if it's > 100%

[steve]

If the result of the calibration is < 0, 0 is used. If the result is > 100, 100 is used.

[nking]

I see, therefore a thought springs to mind (I’m probably the last person to have thought of this!) regarding Fine Offset users.
These units max out at 99% and I imagine this is why you’ve provided the option in the Configuration screen “Use 100% for 98% Humidity” however, this means that 98 and 99% are never reported.
F/O units are not known for their accuracy therefore, it would be better to use the Calibration section (assuming the figure reported by the F/O is <= actual) to be able to report 100%.
If you are lucky enough to have a sensor that is accurate (highly unlikely) then adding 1% to the calibration would allow you to report 98,99 and 100% - a margin of error that would be very acceptable I would say.

I hope this makes sense

[steve]

These units max out at 99% and I imagine this is why you’ve provided the option in the Configuration screen “Use 100% for 98% Humidity” however, this means that 98 and 99% are never reported.

That option is really for the older Oregon Scientific stations, which never report above 98%. As you say, the best way to achieve 100% with FO stations is probably with a +1 calibration.

[wd40]

If I adjust my humidity by -6, will it ever get up to 99%?

I am curious. Did you do like a wet bulb test to check your weather station?

[ironeagleuk]

If I adjust my humidity by -6, will it ever get up to 99%?

I am curious. Did you do like a wet bulb test to check your weather station?

No I didn't....I was comparing it to stations nearby on this site: http://www.awekas.at/en/temp.php?nid=10

As mine was showing 99%, and others not too far away from me were showing less than 93%

[wd40]

Richard, it could be your station was recording accurately. Humidity can vary with location over very short distances, by elevation from the ground as well as its surroundings.

[ironeagleuk]

Richard, it could be your station was recording accurately. Humidity can vary with location over very short distances, by elevation from the ground as well as its surroundings.

I suspect you're right, and am just worrying about nothing really
I've decided to change it back....as am sure not being able to report at least 99% humidity is worse than being out by around 7%

[Ned]

Correcting humidity simply by adding a multiplier or offset results in distortions at the top end of the scale i.e approaching 99% (where I want it to be about right, assuming the instrument isn't too far off there)
I've been playing with a correction factor that is manually applied via spreadsheet using the difference beween 99% and the instrument reading, so the greater corrections occur when humidity is low, and disappear at 99%. Improvements have been gained to my F.O. readings (compared to a sling psychrometer), but it'll never be 'right', as the humidity data of these stations would only be really correctable by using lookup tables individual to every station.
Having said that, I'd still like to see a correction offset provided for internal humidity, which consistently reads about 10% low (over the relatively narrow range of internal conditions)

[ironeagleuk]

My in-accurate humidity reading seems fairly apparent today compared with those stations around me if you look at this site: http://www.awekas.at/en/qualcheck.php?art=hum&id=8883

At least the plotline is the right shape....just abit too high on the scale

[mcrossley]

A multiplier of 0.78 will get you pretty close, most reading within +/- 1, with a couple of outliers (max 3.26)