An EMF meter can measure AC electromagnetic fields, which are usually emitted from man-made sources such as electrical wiring, while gaussmeters or magnetometers measure DC fields, which occur naturally in Earth's geomagnetic field and are emitted from other sources where direct current is present. Manual Data Memory : Records Maximum & AVG Memory Recall : Adjustable Sample Time : 2.5 times per Second Alarm Function : Adjustable Threshold ON/OFF Measuring Units : mV/m, V/m, ?A/m, mA/m, ?W/m² , mW/m², ?W/cm.