A number of different methods for DC and AC magnetic field (MF) measurements are used. The most sensitive magnetometers are based on super conducting quantum interference devices (SQUIDs). A major drawback of these instruments is their extremely low operating temperature. Optical methods are also used, and recently the possibility of applying Coherent Population Trapping (CPT) effect for weak MF measurement was emphasized. The aim of this project is to carry out theoretical and experimental research to explore the potential of the CPT effect for precise MF and electromagnetic field (EMF) measurements. CPT based magnetometers would operate at room temperature and it is estimated that they would have sensitivity comparable to the SQUIDs' (and better spatial resolution). Prototypes of small portable CPT devices for general MF measurements and for applications in medicine and industry should demonstrate the possibilities of this new technique.