Rad-X is a portable ionizing radiation detector meant to measure background ionizing radiation, and is in essence a Geiger-Müller counter. A Geiger-Müller counter derives its name from its measurement component, the Geiger-Müller tube that is used to detect radiation. A Geiger-Müller tube generally comprises of a tube that is filled with inert gas kept at low pressure and with a high voltage applied across the tube.

When ionizing radiation ionizes the gas in the tube, an electric charge is sent through the tube and this ionization will be amplified to create an electric pulse. This electrical pulse is then recorded and processed into meaningful data.

Rad-X is able to output two kinds of results: Counts and Radiation Dose (Sv). Counts is the number of ionizing events recorded with units usually as Counts per minute. Radiation dose is reported in Sieverts, which is a unit used to represent the stochastic health risk due to ionizing radiation. As small doses of radiation are stochastic in nature, a dose measured in Sieverts represents the probability of radiation-induced cancer or genetic damage.