The parallel plate ionization chamber PPC40 is designed for absolute and relative electron beam dosimetry above 2 MeV in the measuring quantity absorbed dose to water. It can be used for proton beam absolute and relative dosimetry and for photon beam depth-dose measurements as well. The PPC40 is entirely made from PMMA; with graphitized electrodes. It is constructed with a circular sensitive volume of planar geometry covered by a rigid 1 mm thick entrance window. As an associated measuring instrument for precise absolute dose determinations, in reference dosimetry, compliance testing or installation and set-up of treatment machines or other equipment, it is recommended to use the reference-class therapy dosimeter Dose1. The PPC40 is waterproof and its cable is covered by a watertight silicon sleeve that allows for air ventilation.