The EM3 unit is a multi-function, low frequency, broadband EMF meters that measure AC Electric and AC Magnetic Fields.   These devices are designed to have a wide dynamic range with high sensitivity. They can also be referred to as Electric Field Meters, Tesla Meters or Gauss Meters.   They accurately measure the invisible emissions that radiate from electrical wiring and devices that use power. 

Also, the EM3 is more sensitive, has a higher frequency response, and includes the ability to measure body voltage.