In this work, we propose the development and the application of a numerical model to simulate the electrical characteristics of polycrystalline diamond conceived for sensors fabrication. The model is based on the introduction of an articulated, yet physically based, picture of deep-level defects acting as recombination centers and/or trap states. This approach fosters the exploration and optimization of innovative semiconductor devices conjugating the capabilities of CMOS electronics devices and the properties of diamond substrates, e.g. for biological sensor applications or single particle detectors for High Energy Physics experiments.