Charles Laforge wrote: >Out of curiosity... have you tried the solid state wind speed sensor >which appeared in (the latest?) electronics now? I don't have the mag >here with me but I figure someone must have tried this. What type of >accracy can one expect? I have built the device, which is a hot-wire anemometer. I left out the digital section, since I'm feeding the output to an ADC and into a PC. (Not a PIC, because I don't know how to use PICs. Why am I on this list? Because I would eventually like to port my whole weather station to a PIC based system. so I won't have to leave a PC running all the time....) As Bill Rininger mentioned, the device's response time is a little slow, though I don't know how it compares with a mechanical cup anemometer in that respect. I don't have a good handle on accuracy, since I don't have access to a wind tunnel. Using the "stick it out of the window of a moving car" method of calibration ain't as easy as it sounds. First of all, it's very difficult to maintain a very constant speed in a typical automobile (at least *my* automobile). Any small dips or rises in the road affect the data noticeably. Second, automobile speedos are not made for great precision. Third, the calibration method assumes zero ambient wind speed, which simply isn't realistic most of the time. All of these factors, and perhaps others that I haven't recognized, made it very difficult for me to calibrate the unit to better than +/- 5 mph. Another slight problem is that the unit, even with the log amp, does not seem quite linear. This flaw is potentially easily dealt with, provided that one can somehow come up with a good plot of output vs. wind speed. Back to the wind tunnel. Another drawback of the hotwire anemometer is that it must be shielded from rain, snow, direct sunlight, and anything else that will cause heating or cooling. The shield must not interfere with normal airflow. BTW, I want to thank Tom Handley for his stellar post on PIC weather stations. Steve Turner