Atmospheric Electricity Detector
Approx construction cost US$30
The ionized layers of the atmosphere extend from about 40km to 200km (25 to 125 miles) above the earth. This ionization is caused by the "Solar Wind" passing the earth and leaves the upper atmosphere positively charged.
There is thus an electric field between the upper atmosphere and the earth. Using suitable instruments, this field can be detected as it results in a minuscule current through the atmosphere.
If a probe, consisting of a metal plate, is supported on an insulator one meter above ground the metal plate will acquire by conduction the same potential as exists at this level above ground. This would be true of any height, of course, but the meter is a nice standard unit.
A potential of around 100 volts is often present. In other words there is often a potential of 200 volts or more between your nose and toes! Of course nobody gets electrocuted because the resistance of the air is so high that only a very tiny current is present. This is why the actual values are so difficult to measure, but the author sets out to do so in this rather interesting experimental article.
More details on this construction project can be found in the June and July 2000 issues of EPE Online, the world's first web-delivered electronics and computing hobbyist magazine.
PURCHASE this issue or peruse more Projects