Updated: May 12
A lot of good folks believe that EMF is like a fog or small waist-high floating cloud they can sweep their EMF detector through and get a hit. This is not so. EMF is not like a small floating cloud. EMF is an alternating current radiating from the source. The source could be a radio tower or your Rumba.
Geomagnetic or DC magnetic fields do not alternate and are therefore not detected by an EMF meter detector. An EMF meter will not detect a magnet from your refrigerator. Unless you can move it back and forth fast, then it would be alternating current.
The earth's magnetic field is stable, static, it does not alternate. This is one reason most EMF meters do not detect this magnetic field. Parts of the Earth change. Areas are heated by the sun and plates move causing changes in the earth's magnetic field. This change causes alternating current. Your EMF meter would detect this as an EMF.
How to tell the difference between EMF and geomagnetism. You can tell the difference if you have the right equipment. A meter that detects DC magnetism is one you need. You cannot move these around, they must be stable and static to read properly. Compare your analog EMF meter detector to the DC meter. If they both react, it is geomagnetism. If only the EMF reacts then it is EMF not from the earth.
You should remember that the direction of magnetic field lines around a current carrying wire is circularly perpendicular to the wire. So alongside the wire, the field lines are vertical, while underneath the wire, the field lines are horizontal. The proper orientation of a single axis meter may point the meter at the wire, or straight up and down, or even horizontal, depending on the orientation of the sensor in the meter and the position of the meter relative to the wire.
Because magnetic fields are oriented in space, a sensor will only detect the field properly if it is aligned with the field. A single axis meter has only one sensor in it. Therefore to get a correct reading with this type of meter, you must slowly rotate the meter until you find the maximum. This will be the correct reading. If the meter is turned 90° from the maximum reading, it will read zero. See Pro 1-Axis Gauss Meter for an example of a 1-axis gaussmeter. It is easy to understand how you can get a lower than actual reading if the meter is not properly aligned.
A three axis meter has 3 sensors in it, all aligned at right angles to each other. Therefore, this type of meter is always correctly aligned and no rotation is required to get a correct reading. This type of meter takes less time to use but generally costs more than its single axis counterpart. See 3-Axis Digital Gaussmeter and Trifield Meter for examples of 3-axis gaussmeters.
In the paranormal, detecting spirits with an EMF detector is theoretically possible. If a couple of things happen. The spirit would have to radiate at a frequency the EMF meter can detect. The Spirit would have to radiate alternating current. If these two happen most EMF detectors could detect spirits.
What happens when you feel static, and your hair stands up? This is where a high-quality EMF meter is handy. You can switch the EMF meter to DC detection and detect the static.