From: Jim Thompson
Subject: Re: Rain intensity to voltage idea... Opinions?
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Date: Fri, 04 Oct 2002 21:45:38 GMT
NNTP-Posting-Date: Fri, 04 Oct 2002 17:45:38 EDT
Organization: Cox Communications
On Fri, 04 Oct 2002 16:21:21 -0500,
In Newsgroup: sci.electronics.design,
Entitled: "Re: Rain intensity to voltage idea... Opinions?",
Wrote the following:
|On Fri, 04 Oct 2002 19:23:22 GMT, Jim Thompson
|, masquerading as a MSNBC reporter, said
|the following to White House press secretary Ari Fleisher during a
|press conference concerning the New War:
|>(1) Capacitor microphone, amplify noise, rectify and filter output.
|Yeah, great for days where the birds are making more racket than the
|cicadas and katydids, which is quite impressive to behold out here...
|Potentially workable, but I just don't like the idea of non-rain
|events causing a jump.
I had in mind constructing your own capacitor microphone with such
gross dimensions that only a surface impact would create a signal.
|>(2) Bucket with small hole in bottom, then measure height of water in
|Then I need electrodes in the water to allow me to graph depth. Every
|so often I need to clean the electrodes or recalibrate... Remember, we
|are talking rainwater here, not microfiltered, deionized bottled
Use a tapered vessel so you get a logarithmic output.
|Here's an interesting method along the lines of using probes. Use
|carbon pencil leads (like drafting compass refills) instead of metal
|for a resistance that decreases as the water level rises. Bad points:
|The carbon probes will still eventually need cleaning or replacement,
|and carbon is quite brittle. Also would probably regularly need to
|clean the surfaces where the wires contact the probes. My brother gave
|me the idea for this when we were kids. He went though a phase where
|he was in love with hydrolysis, and made little pencil carbon arrays
|to greatly increase the surface area of gas production without
|corrosion on the electrodes. It occured to me that a typical variable
|resistor is just a wiper contact along a carbon track, and a long
|pencil lead would make a great depth probe.
You probably can make capacitance work, *except* you will need to
slope it to allow for run off, and calibrating may be difficult.
| - NR
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| Jim-T@analog_innovations.com Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
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