I didn't think of it until Thomas Hillson <[EMAIL PROTECTED]> spaketh thusly, but:
> None, of the simple thermometer/hygrometer systems I have > seen are very good, I have bought lots of them. If you > want an accurate measure of temperature and humidity you > need a high quality weather station system or a good wet > bulb/dry bulb hygrometer. ... > One system I have used is from Sensatronics. It is a handy > multi probe system you can hook up to monitor your > greenhouse, I have one monitoring my greenhouse and I too > two probes and set them to a wet bulb/dry bulb system to > track the humidity in my greenhouse. I had to read this a couple of times, and thought I should underline this for those that might not understand. There are several ways of determining relative humidity; shy of employing a gas chromatograph, a sling psychrometer is the most accurate technique that may be readily employed. An alternative to swinging two thermometers around your head to find out what the humidity is would be to take two thermometers, one with a wetted wick on its base, that are fanned constantly (or, at least, for a minute or so before being read). There are commercial widgets that do just that; they run into the hundreds of dollars, last I checked. What Tom has done is swapped out the thermometers with thermocouples, one of which is the wet "bulb," the other being the dry "bulb." From a psychrometric chart, he can deduce the humidity quickly and accurately; a small computer script could probably do it automatically. I'd be surprised if someone didn't make such a device already, but the price would probably be prohibitive. Very clever indeed, Tom! Cheers, -AJHicks Chandler, AZ _______________________________________________ the OrchidGuide Digest (OGD) [email protected] http://orchidguide.com/mailman/listinfo/orchids_orchidguide.com
