An electricity generating device for use in an armor arrangement, and to an armor arrangement. The armor arrangement includes two inert reactive armor modules arranged one behind the other, which each include a plate made of inert material, interposed between steel plates. Sheet-shaped members are mounted or baked onto the inert material. The sheet-shaped members are provided with a number of mutually separate regions in which, or next to which, there are disposed elements which convert mechanical vibrations or shock waves in the inert material into electrical voltage. The elements can include crystals or piezoelectric layers. The ammunition part or ammunition effect which penetrates the inert reactive armor modules and which generates the mechanical vibrations or shock waves provokes in one or more elements the generation of a voltage which can be used to initiate counteragents against the penetration.