An electromagnetic field meter, or EMF meter, is one of the most popular pieces of ghost hunting equipment. They are simple to use, often consisting of nothing more than an on/off switch. They alert you when they detect an electromagnetic field from 50 to 20,000 Hz. This means it picks up the part of the EM spectrum with a wavelength ranging from about 14 to 6,000 km. The device gives instant feedback via a digital display or LED indicators, usually five.

An EMF meter can be used to communicate with spirits during a séance. When using an EMF meter, you should call out to any spirits that might be present and encourage them to come forward and try to trigger the lights on the meter in order to show that they are present or to indicate an answer to a question.

There is no scientific understanding of how spirits can communicate using...