GENERAL DIAGRAM OF THE GEIGER COUNTER

    The Geiger detector is a tube filled with a gas. A high voltage is applied  to the Geiger tube. The radioactivity ionize the gaz inside the Geiger tube, and an electric discharge appears. Each electric discharge create an electric pulse amplified and counted by the electronic of the display. The radioactivity level is measured by counting the electric pulses outgoing from the Geiger tube. The high voltage applied to the Geiger tube is approximately 500 volts, two resistances and one condensator are used to detect the signal and protect the Geiger tube.