In the present article we analyze a vacuum microelectronics magnetic sensor based in a simple configuration with a double-gated wedge emitter with a split anode as current detector. The actuation of such device has been simulated using several numerical approaches including full determination of electrostatic potentials with accurate description of fields at the wedge region, electron beam propagation inside the device, and evaluation of the current density distributions at the anode detector screen. Calculated sensor sensitivities are larger than those found in conventional magnetic field sensors designed to detect similar magnetic field ranges. The focusing system provides a tuning mechanism able to change the sensor sensitivity and the magnetic field detection working range. The dependence of the sensitivity on geometrical parameters and control voltages is discussed.