A radio and microwave detector is also included, which reads radio power directly. Because man-made AC (alternating current) electric and magnetic fields are very common and could interfere with readings of static fields, the meter has been designed to ignore AC fields. Normal construction materials don't block magnetic fields, so the meter can be placed indoors and will work equally well, and due to the built-in tone, it can be used in the dark, and will sound the tone at whatever level of field the user sets. It operates on a standard 9-volt battery. Therefore, the “battery check” feature must be used prior to investigating.
The meter is sensitive to changes of as little as 0.5% of the strength of the Earth's magnetic field, and the tone will sound whether the field increases or decreases. This meter can also be used to determine if anything is magnetized. The Natural EM Meter can detect geomagnetic storms caused by unusual solar activity interacting with the ionosphere (which results in rapid changes of up to 10% in the Earth's magnetic field), as well as the electrical activity of ordinary thunderstorms. It will signal the movement of any distant, strong magnetic sources in the sky, even if the sky is cloudy or the source dips behind a hill. When the dial is set to ELECTRIC, the meter is sensitive to electric fields as weak as 3 V/m (volts per meter). Human beings and animals usually emit an electric field which is easily detectable using the Natural EM Meter. In fact, the meter can be used as a motion-activated intruder alarm.
Type of Energy Effect or Field RADIO/MICROWAVE The radio/microwave detector is sensitive from 100,000 to 2.5 billion oscillations per second (100 KHz to 2.5 GHz) and can detect strong or unusual atmospheric electrical activity. It can also detect leaky microwave ovens, cellular or portable phones, walkie-talkies and concealed surveillance bugs. Its minimum and maximum detectable signal strengths are 0.01 milliwatt/cm2 and 1 milliwatt/cm2 respectively.
The SUM setting adds together the electric and magnetic fields and detects if either field changes. The meter is used to find a disturbance in either type of field, but in the SUM setting it can generally detect if a person approaches to within five or ten feet, even on the other side of a wall. For this reason, this model is preferred for parapsychological research, when, for example, a room to be measured is known to be vacant for an extended period (except for experimenters, who remain relatively still for that period).