A lot of ghost-hunting gadgets claim to use electromagnetic detection methods to detect ghosts. This is a bold claim when you consider that there aren't even any devices that are capable of detecting a living human based upon their electromagnetic signature alone. However, humans do create a magnetic field and emit EM radiation, but they are very weak. For comparison, the magnetic field of the Earth is just strong enough to move the needle of a compass. Signals from the brain are a billionth of that strength.

This magnetic field can be measured using an instrument called a Superconducting Quantum Interference device. The experiment is normally conducted in a magnetically shielded room to filter out external interference. Various parts of the body can be measured. The heart generates the largest electromagnetic field in the body. The magnetic field from the brain is called the magnetoencephalogram, or MEG.

The body's internal magnetic field...