This paper describes in detail an efficient simulation tool for rotors on magnetic bearings suitable for application on turbomachinery in the gas and oil field. Unlike roll bearings, magnetic bearings are active systems that need special treatment for assessing their stability and robustness, that strongly depend on the dynamic behavior of the other components of the system (actuators, sensors, etc.). In this sense, sensors are critical components in these systems because of their variation in sensibility in time and the difficulty in assessing their real parameters. This simulation tool is designed to help in the choice of sensors for a given system in order to assess its suitability.