William, I'll apologize in advance. Meteorology is sort of my thing, and sometimes I can't help myself... :-) Actually, that's not all that bad. I'm betting your recorded temperature variation would be an inverse function to the RH. RH is very dependent on the ambient temperature. Colder air holds less moisture so it'll have a higher RH. Warmer air can hold considerably more moisture. So, even though the RH fluctuates, the amount of moisture in the air is probably relatively stable, unless of course a front is moving through, etc. If you want to see fluctuations in actual moisture, watch the dewpoint temperature. That's the temperature at which the existing moisture in the air would have to be cooled to, in order to reach 100% saturation. In a home, I think we watch the RH more because the ambient temperature is relatively stable, so fluctuations in RH would reflect an actual change in the dewpoint, or the actual amount of moisture in the air. Regards, Rob McCall McCall Piano Service, LLC www.mccallpiano.com Murrieta, CA 951-698-1875 On Aug 24, 2010, at 05:51 , William Monroe wrote: > Hee, hee, > > Try WI. I have a pretty advanced weather station on my property, and regularly monitor the outdoor RH (and contrast that with thin indoor). I don't have central AC in the house, but it stays much more constant than outdoors. Yesterday, the outdoor RH went from 92% at 8am, to 56% at 6pm, to 89% at 10pm. It doesn't always change this fast, or frequent, but daily fluctuations are often in the 30% range. Indoor fluctuations (running some window AC units occasionally) are more on the order of 10% - 15%. > > William R. Monroe
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