Abstract: A Hall voltage device including means for generating a magnetic field and a rotatable box mounted within the field in the air gap defined by the means. The box is arranged to receive a fluid including charged particles and comprises appropriately located electrodes cooperating with the fluid and means for rotating the box. An end face of the box is provided with a central aperture around the axis of rotation for introducing the fluid into the box. In another embodiment the apparatus comprises a pivot having two parts, each part connected to a respective electrode of the box. Each part contacts an amount of mercury contained in a reservoir. The two reservoirs are connected to a voltage meter. Cooling means for the mercury reservoir is also disclosed.

Abstract: A Hall-voltage device in which a rotatable box is disposed in the air gap of a magnetic circuit. The box is arranged to receive a fluid having charged particles distributed therein, which fluid can cooperate with electrodes. One end face of the box is provided with an aperture through which a thin, flexible disc of plastic foil, which serves as the electrode support and has a radial cut, can be inserted into the box. The disc is provided with electrodes and associated discharge conductors and can be fixed in the box by means of a pivot extending through the aperture, which pivot includes terminals to which the discharge conductors extend.