ml>> how can one set up their own "shadetree mechanic" type
 ml>> of instruments like the wet bulb thermometer? is it
 ml>> just a matter of having two thermometers the same and
 ml>> mounting out with a cloth that is soaked with water?

 HT> Yes.  In this case, two electronic temperature sensors.  A fan
 HT> is also required to fully depress the wet bulb reading.

can you give details on this? maybe even circut designs? i'm pretty handy
with a soldering iron and copper clad board with etching pen and chemical
;)

 ml>> i've been by several weather related sites looking at
 ml>> their machines... we've been wanting to have something
 ml>> out here for a long time but the cost has always been
 ml>> prohibitive...

 HT> I've got a very inexpensive Radio Shack instrument that
 HT> measures humidity.  It's very precise, but did require "shade
 HT> tree mechanic" work to make it accurate.  I connected a
 HT> variable resistor in parallel with the sensor and adjusted it
 HT> until I got readings that pretty much matched my wet and dry
 HT> bulb measurements using a conventional sling psychrometer and
 HT> chart.  Finally, I soldered the appropriate-sized resistor in
 HT> paralllel to the sensor, put the cover back on it, and mounted
 HT> it on  the wall.  It's worked famously for several years now.

 HT> I'm THE humidity-measuring guru on campus.

i hear ya! i'm looking not only at doing the humidity but also temp and
wind dorection and speed measurements... had thought one time to just take
a bicycle speedometer to use as a calibrator and put magnets on a set of
homebuilt cups and count rpms and convert to mph... direction would be a
tad more involved... i remember two three pole devices such that when you
moved one the other followed but it took three poles to do it... dunno how
that'd be handled electronically if it'd be done that way at all...

)\/(ark