Martin, tipping bucket rain gauges are fairly standard for measuring
rainfall. The basic design is a collector that funnels the water into a
small orifice that fills the `buckets'. Simple designs use a magnet
that closes a reed switch. I designed a PIC-based weather station around
four years ago and I use a Davis Instruments rain gauge where each `tip'
triggers an RB0 interrupt. Since I live in the USA, each `tip' equals
0.01". Davis sells these for around $60 and it has proven to be very
accurate here in Oregon where we get a lot of rain. There are also kits
and plans out there.

   Back to the original message, a `rain detector' is simply two probes
or a PCB with traces in a serpentine pattern.

   - Tom

At 04:04 PM 8/26/99 -0500, Martin McCormick wrote:
>        One rain measuring method we studied in a Physical Geography
>class I took once is called the tipping bucket gauge.  A rod is
>connected to a shaft that can turn a counter and probably also
>provides some detent to position it correctly.  The rod is normally
>vertical with a small bucket on each end.  At any given time, one
>bucket is pointed toward the sky to catch water and the other one is
>upside down and empty.  When the top bucket fills, the weight flips
>the rod which increments the counter, spills the full bucket and
>brings the other bucket up so it can fill.  The process continues and
>the counter counts the number of buckets filled.  Such an arrangement
>could be easily adapted to use a PIC as the counter.
>
>        We studied this briefly in class and the instructor said it was
>used in areas that get lots of mist.  I am not sure how well it would
>work in high wind.
>
>Martin McCormick


------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)