The range of devices used for ghost hunting helps measure electromagnetic fields to identify devices that produce high levels of radiation and enables users to determine the extent to which to limit exposure. Colored LEDs make readings visible in daylight or darkness; easy to carry all the time since it fits in your pocket or purse.Levels are measured to prevent potentially harmful long-term overexposure to electromagnetic fields.The ghost hunting detector operates on a single battery and reports EMF measurements in the range of 5 mGyS.Measuring various electromagnetic fields from 50 Hz to 20,000 Hz, it can register cell phones within 2 feet.