An entire microsystem for high accuracy magnetic field measurement based on vertical Hall devices has been simulated. In accordance with existing knowledge about semiconductor physics and experimental results, a functional SPICE- model for a vertical Hall device has been developed. This model was then applied to simulate an existing high accuracy magnetometer, including temperature and non-linearity compensation. The comparison of simulated and measured results shows that the real physical effects as well as the behaviour of the signal treatment electronics have been correctly implemented.