Extech SDL900 Handheld AC/DC Magnetic Field Meter/Datalogger is designed to measure and datalog both AC and DC magnetic Field in Gauss and mT (milli Tesla) via an advanced uniaxial Hall effect sensor with integrated ATC. The Extech SDL900 features datalogging up to 99 readings, user-adjustable sampling rates (1 to 3600 seconds), N pole and S pole indication, MIN/MAX functions, and more.