The Extech EMF510 detects energy from electromagnetic fields (EMF) and electrical impulses, and it is sensitive to extremely low frequency levels. The built-in single-axis sensor can monitor power lines, electrical appliances, fans and blowers, and electrical circuits in two ranges: milli-Gauss and micro-Tesla. The EMF510 has a wide backlit LCD for readability in low-light environments, an ergonomic compact design with a wrist strap, auto power off, and a Min/Max function.