Abstract: A personal radiation monitor worn by a person who may be exposed to potentially harmful radiation includes a main unit and a radiation sensor cartridge which is matable with and removable from the main unit of the monitor. The removable sensor cartridge includes one or more radiation sensor elements for detecting radiation, and further includes an electronic memory having stored therein calibration and identification information relating to the type of radiation and/or frequency bands of radiation which the sensor or sensors are designed to detect. The sensor cartridge is easily removable from the main unit of the monitor so that one sensor cartridge is interchangeable by the end user with another sensor cartridge.