A gaussmeter, also known as a magnetometer, is a device used to measure the strength and direction of a magnetic field. Small, hand-held versions are available and the user can carry it with him to monitor magnetic fields as he walks. The device may also be referred to as an electromagnetic field detector, or EMF detector for short. The device has several scientific uses and is popular among paranormal researchers.
Two types of gaussmeters exist: scalar and vector. The scalar gaussmeter measures the strength of the magnetic field present in the area around the device. The vector gaussmeter measures the direction of the magnetic field depending on where the device is and which direction it's pointing. A gaussmeter may combine both of these technologies.
Using a gaussmeter is a fairly simple process. The screen provides a reading of how strong the magnetic field is and may indicate the direction it’s coming from. If the person holding it walks closer to the magnetic source the reading will rise; it will lower if the person walks away from the source. Multiple sources can create conflicting readings, however, and may require more advanced technology to determine where the sources are coming from.