In the nuclear research field, the measurement and the knowledge of the nuclear heating are crucial to carry out fine studies on accelerated ageing of materials and the behavior of nuclear fuels under irradiations with in particular accurate imposed temperature conditions. Nuclear heating can be quantified thanks to a differential calorimeter by using in-pile temperature measurements and preliminary out-of-pile calibration curves of each calorimetric cell. This paper focuses on experimental studies of two new calorimetric cell prototypes developed to test the influence of the Joule effect heating of specific cell body areas on the out-of-pile-calibration curves. The calibration curves are determined, discussed for different applied internal/external thermal conditions and compared to irradiation data obtained with the CARMEN-1P type calorimeter used into the OSIRIS reflector.