This chapter presents the basics of radiation detection. Radiation detection equipment "counts" the ion pairs created. Radiations of different type and of different energy will create different numbers of ion pairs per path of radiation. A radiation detection instrument will detect several energies of radiation passing through its detector and will show response on the instrument but will measure only the energy it is calibrated to measure. In addition to the type and energy of the radiation, the type of material exposed to the radiation will play a part in how many ion pairs are created per path. The electroscope design feature of the self-reading dosimeter is what permits it to detect the accumulation of radiation rather than the rate of radiation exposure. If ionizing radiation passes through the area of the metal strips, the negative charges created by the ionizing radiation will neutralize the positive charges on the metal strips.