Several novel field emission devices are analyzed in a unitary way. The devices involve the use of field emitter arrays in a special configuration where the emitted electrons are subject to crossed electric and magnetic fields. Due to the acting electric and (magnetic) Lorentz forces, the electrons are either deviated or have a cycloid-like confined motion. The angular deviation of the electron trajectory can be used for measuring magnetic fields. The pulsed electron current produced by a cold cathode can be used to generate electromagnetic radiation. Because the electrons have a confined motion with a long trajectory length, their chance of hitting a residual gas molecule is increased. They can either excite gas molecules, which in turn emit UV-radiation when relaxing back to the stable state, or ionize them, the ionic current being correlated with the gas pressure. Accordingly, devices for generating UV-radiation and vacuum gauges can be devised. Furthermore, if the ion generation takes place in a narrow and well-defined region, then their angular deviation can be correlated with their mass. A mass spectrometer (with miniaturized dimensions and field emission electron source) can be devised on this principle.