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Author Topic: How is humidity measured?  (Read 144 times)

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Offline dan43

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How is humidity measured?
« on: November 14, 2017, 07:04:47 PM »
I know this sounds like a dumb question, but I'm curious as to why humidity is sometimes measured at max. 100% and other times it's measured at max. 99%?  Right now when I look at my humidity chart, it shows me all of my maximums at 99%, when I'd like to see if I can change this to 100%.  Is there a true value for 100% humidity, and isn't it simply that the air is saturated to its maximum vapour pressure?

Can I tell WD to display the true value?

Offline Weather Display

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Re: How is humidity measured?
« Reply #1 on: November 14, 2017, 07:23:20 PM »
depends on the quality of the sensor used (and station type you have) if a 100% measurement will ever be seen
this is a hardware thing and not a software thing
but you can set in WD to set 98 or above as 100% (see in the offsets/humidity)

Offline dan43

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Re: How is humidity measured?
« Reply #2 on: November 14, 2017, 07:30:56 PM »
Thank you Brian, I did see where I can set the offset 98/100, but I don't think I want to tinker with something I've had a in place for almost 2 years.  I think I can live with it the way it is now.  Many thanks for your prompt reply!

Dan

Offline Jachym

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Re: How is humidity measured?
« Reply #3 on: November 15, 2017, 03:54:05 PM »
depends on the quality of the sensor used (and station type you have) if a 100% measurement will ever be seen
this is a hardware thing and not a software thing
but you can set in WD to set 98 or above as 100% (see in the offsets/humidity)

I know about this problem, it is as Brian said a HW issue. But Im just wondering, does this mean that in such case you will never have 98 or 99 in WD and it will jump from 97 directly to 100? because very often I have 98 or 99, and that would not be possible to tell the difference

Offline Weather Display

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Re: How is humidity measured?
« Reply #4 on: November 15, 2017, 05:38:28 PM »
that feature is there for where some older weather stations would never go above 97%
the new WeatherFlow station reports 100% where my Davis will not (although I do not have the latest sensor available for my Davis)

Offline dan43

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Re: How is humidity measured?
« Reply #5 on: November 15, 2017, 10:01:16 PM »
I know about this problem, it is as Brian said a HW issue. But Im just wondering, does this mean that in such case you will never have 98 or 99 in WD and it will jump from 97 directly to 100? because very often I have 98 or 99, and that would not be possible to tell the difference

My humidity chart shows me 97%, 98% and 99%, but in two years of running my station, it's never hit 100%.  Out of sheer curiosity, I've just set the humidity settings so that when it reaches 98% to display it as 100%, but if I don't like the results once I've had a chance to see a couple of instances, I'm switching this option off.

Obviously, the WMR300 won't display 100% by itself.

Dan