Scintillation counter: It measures ionizing radiation. The sensor, called a scintillator, consists of a transparent crystal, usually phosphor, plastic, or organic liquid that fluoresces when struck by ionizing radiation. A sensitive photomultiplier tube (PMT) measures the light from the crystal. The PMT is attached to an electronic amplifier and other electronic equipment to count and possibly quantify the amplitude of the signals produced by the photomultiplier. Geiger counter: Is a type of paicle detector that measures ionizing radiation. They detect the emission of nuclear radiation: alpha paicles, beta paicles or gamma rays. It detects radiation by ionization produced in a low pressure gas in a Geiger Muller tube.