Contamination detectors with ZnS scintillators use a single scintillator made of zinc sulfide (ZnS) to measure the radioactivity. The radiation to be measured strikes the scintillator. The resulting flashes of light are conducted by a suitable reflector to a photomultiplier with a suitable preamplifier and discriminator stage and measured. Using special evaluation and correlation circuits, the individual types of radiation such as alpha and beta/gamma/X-ray radiation are distinguished, separated and measured simultaneously (patented by BERTHOLD). Part of the spillover of alpha particles into the beta channel is corrected by software.