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Earth Magnetometer

http://scientificmeter.com

Used in conjunction with the Hartmann Line Information

Geomagnetometers, such as this meter, are usually used to measure the strength of earth's field at several points on the land surface. These points are sometimes arranged in a square grid (with spacings such as 10 x 10 feet). In this case, a measurement is recorded at every point on the grid, and a map can be made from these numbers. The map might show for example, that the field is stronger in a circular area about 20 feet in diameter in the center of the grid than it is at the edges of the grid. This would suggest that a magnetized object is buried roughly 20 feet underground.

Instead of measuring on a square grid, measurements are sometimes made at several points along a straight line. The relative strength of field is measured at each point (relative to the field strength at the starting point). If there is an area with a stronger (or weaker) field than average, then the place along that line where the field is strongest (or weakest) can be found with the meter. Then measurements are made along a straight line that is perpendicular to the original line, starting at that strongest (or weakest) point on the original line. If you're looking for the location of the strongest (or weakest) field, this method is faster than measuring every point of a grid.

All types of geomagnetic meters require that you point them, at least approximately, in a certain direction (with respect to the earth's field direction). Otherwise the readings will be inaccurate. With a proton magnetometer, the sensor can be pointed as much as 30° off from the preferred direction before the readings start to become noisy. It's easy to keep the sensor pointed with +/- 30° of a certain direction when measuring in the field, so this is not much of a problem. However, the AlphaLab Earth Magnetometer is a vector magnetometer, and it must have its sensor pointed (at least momentarily) within one-third of a degree of the correct field direction in order to measure the actual field to .01 milligauss precision. This kind of precision required in pointing the sensor had been a problem when using vector magnetometers to measure the exact earth field strength. A “fluxgate” magnetometer (which is also a vector magnetometer) could have been available a long time ago as a less expensive alternative to the proton magnetometer, had it not been for the accuracy of pointing needed.

The Earth Magnetometer also has a rapid scan function. This is only sensitive effectively down to 1 milligauss (but theoretically down to 0.1 milligauss, or 1/50 percent of the earth's field). It allows you to walk along, continuously reading the field. You can see “blips” as fast a 1/10 second.