WTD: electric field mill, maybe a Boltek

Also known as generating voltmeters. They are used in electrostatic particle accelerators to measure the DC terminal potential.

What kinds of fields/gradients are you looking at?

----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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The sort of stuff associated with weather, day to day and the occasional thunderstorm, perhaps 100 to 1000 volts/meter.

There are a variety of web pages describing how you can try to build one of these yourself. Scientific American, Amateur Scientist, published one in 1999 I think and there are others out there. (but with my mechanical skills I think that trying to build something to spin one metal garbage can inside of another and in close proximity and at 7000 rpm would earn me a spot on the "World's Stupidest Person" television show somewhere)

I'm also looking for a magnetometer for geomagnetic field variation measurement.

Anyone know of a source of either of these, perhaps used?

Thanks

Don-

Because of the threat of damage to launch vehicles, field mills have been used extensively for lightning research and prediction at the Kennedy Space Center. If they didn't invent them, they probably improved them.

There is a chance you can find some old ones that were replaced or upgraded. Check out

If you can find reports published by some of the researchers, there may be e-Mail addresses you can contact for more information. Someone working there might be more aware of when equipment is to be replaced or upgraded. If you are associated with a university research program, it might be possible for them to transfer surplus property directly instead of auctioning it off.

Fred

The space above it, actually. Air isn't needed.

Boltek makes these. Others would be

Take a look at New Mexico Tech Langmuir Lab website. Their EE department build them. Plenty of detail, including circuits. They're not difficult to make, if you have machining facilities (or even if you don't, and don't mind a bit of crudity). Calibration is a breeze.

One day, I shall do one. Probably after the Schumann resonance antenna :-)

Okay, that's a lot lower field than one sees in particle accelerators, so you'd need larger rotors and/or faster rotors.

;-)

Okay, I see your problem. The ones we used were only about 2-6" diameter and ran at 1800 or 3600 rpm, but this was for fields somewhat above 1MV/m.

----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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