Sounds right to me. The more area you expose to the rain, the more accurately you will record the rain fall. Presumably you could collect the water from your roof provided you know the area it covers and can do the math. Don't use the area of a sloped roof though, only the area it covers. There will be losses of course on something that big, evaporation and probably delay as small amounts get caught on their way to the gauge.
If you drop a few grains of salt into the bottom of the tube enough should dissolve into the water to conduct electricity. Pure water is a very poor conductor of electricity and rain water, though not absolutely pure is well distilled and doesn't contain much by way of ions to conduct electricity. I remember about thirty years ago we had special filters installed in our Medical Laboratory to produce lab grade water through a series of ceramic filters. I don't remember precisely the measurements but they circulated the water through the filters until it offered megaohms of resistance. Most tap water has absorbed sufficient iron, copper and probably many other ions on it's way to the bath tub to very efficiently conduct the electricity from dropping a hair dryer in with your wife. ----- Original Message ----- From: [EMAIL PROTECTED] To: [email protected] Sent: Monday, March 24, 2008 6:24 PM Subject: Re: [BlindHandyMan] give em an inch and Dale: I've got this thing, like Ahab and the whale about building a rain gauge. The problem has been that my understanding of electricity was all wrong. I used a piece of four inch PVC pipe, and put screws in four columns, so that you could read down to the quarter inch. The screws protruded into the inside of the pipe. I used cilacone glue around the screws, and also used that to afix a piece of galvanized metal on the bottom. The plan was to use the pipe like a switch, with a buzzer and a six volt battery. Of course, no way could I get a current through the water, which really astounded me. I had heard about people being electricuted in bath tubs etc. for years. Is there a way to use this kind of circuit principal to read a gauge like this? And, yeah, next time, I'm gonna use a longer pipe and space the holes differently. I figure if I use a funnel that's four times the area of the inside of a cilinder, then having a read point every half inch, I'd be able to read down to the eighth, is that right? Thanks. ------------------------------------------------------------------------------ No virus found in this incoming message. Checked by AVG. Version: 7.5.519 / Virus Database: 269.21.8/1340 - Release Date: 3/23/2008 6:50 PM [Non-text portions of this message have been removed]
