System-level simulations of sensors are valuables for optimizing device and system parameters and validating data-processing algorithms. Nowadays, the tendency of multi-sensor systems has increased the necessity of this type of simulations. In this work, a generic model for simulations of a sensor at system level is proposed. It allows implementing the complete behavior of a sensor including uncertainties and tolerances, nonlinearities, various noises and so on. This sensor model can be customized by extracting information from a datasheet, a power spectral density graph or an Allan deviation graph. Then, simulations of a single sensor or multi-sensor systems can be performed and data fusion algorithms can be tested for different applications.