Robert Redelmeier said:
....
Floyd, I realize you've been unjustifiably flamed, but that
is no reason to reduce your own credibility by misleading
statements.
You also have to realize that I didn't get off the boat here
yesterday. And that *you* have little to no exposure to Arctic
conditions and like a lot of other people your imagination is
good, but doesn't match the reality of Arctic living nearly as
closely as you think.
Yes, arctic outdoor air usually has high relative humidity.
It has to be, otherwise the snow would sublime.
It doesn't????
Now we've had more than one person claiming the relative
humidity in the Arctic is always low, and you claiming it is
always high. I assure you all that it isn't *necessarily*
either, and that in fact it is fairly easy to experience both
conditions in the Arctic.
But that outdoor air is extremely dry in absolute terms.
My psychrometric chart gives 5 grains water per lb dry air for
8'F dewpt. Heated to 60'F, that is 6.4% relative humidity.
You're gonna need big humidifiers and all the fun they are
to maintain (salt build-up, ugh!)
However, if you have *ever* experienced 6% relative humidity,
you know that static just crackles out of everything. You can't
move without generating a charge. Everything you touch gets
zapped. You can't pet the cat, because it will run when you
so much as look at it.
Now, I'm not going to figure out what's wrong with your
calculations, but I have a cat and it jumps on my lap and gets
petted with regularity. So far today we haven't had even one
experience of enough static buildup to cause us to zap each
other (at this temperature, it does happen, though not often).
You can be assured that the relative humidity inside my house is
*not* 6%, or anything close to it.
Furthermore, I suspect that static build-up is more a function
of absolute humidity than relative humidity. Do people have
lots of static problems in Phoenix summers?
Which is to say, you don't have any experience with this at all,
but you're willing to attempt definitive statements??? Tsch
tsch.
I lived in Tucson AZ as a teenager. Trust me, in Phoenix they
have *lots* of static problems in the summer!
I spent 20 years living near Fairbanks AK too.
In Fairbanks the relative humidity can be very low. (However,
at the moment... it's 17F and RH is 91%!) But in Fairbanks
there is no source for water vapor /and/ it is commonly -40C or
colder. Fairbanks sits inland several hundreds of miles, right
between two of the largest mountain ranges in North America;
hence the relative humidity is commonly low, with no wind, and
in the winter there are extreme cold temperatures on a regular
basis. Static is a *big* problem when it gets cold, and only a
small problem with it isn't that cold.
Barrow of course is a maritime environment, and with an ocean on
three sides and with a constant wind there is no lack of humidity.
The relative humidity for outside air is rarely ever very low,
mostly because we rarely ever get extreme cold temperatures here
(due to the moderating effect of the Arctic Ocean and the
constant wind).
The effect is that in Fairbanks static is an almost constant
problem, summer and winter, but in Barrow static is rarely a
problem except during extremely cold weather in the winter (and
virtually never during the summer).
Here are some interesting numbers. I've been archiving hourly
weather summaries from NOAA since last winter. I don't get
every hourly report each day, but in nearly 11 months have 6303
records. A quick grep produces the following numbers:
Total records: 6303
100% RH 354
90-99% 1588
80-89% 2256
70-79% 1872
60-69% 214
50-59% 18
40-49% 1
No records indicated less than 45% relative humidity.
I should probably point out that after 2 decades living in the
Interior, I have a few habits regarding static that are useful.
I use an anti-static mat on the floor and the table my computers
sit on have a grounded metal strip running down the front, such
that as I sit here typing, both of my arms are grounded.
And of course one of the reasons I advocate the use of water
solutions with a wetting agent for cleaning circuit boards is
because of the anti-static benefits (which include the effects
of having a film of wetting agent left on the circuit board to
help dissipate any static buildup, a beneficial effect that lasts
for months).
Incidentally, if anyone can find information on how the
ubiquitous pink anti-static plastic came to exist, the above
reference to leaving a wetting agent on the surface of washed
components has an interesting connection, historically. The
idea of mixing a wetting agent into the plastic mix came as a
result of observing that poly-plastic containers attracted less
surface dirt when they were *not* rinsed clean of soap after
washing. The same applies to computer motherboards.
