Apparatus and method for determining the voltage breakdown and conductivity of particulate material

An apparatus and method for determining both the breakdown voltage and the conductivity of a particulate material, such as a developer material, is provided. In a preferred embodiment, the apparatus for determining breakdown voltage comprises a breakdown cell for storing a preselected quantity of the particulate material and a voltage breakdown ("VB") autometer, the VB autometer being adapted to apply a first voltage across at least portions of the preselected quantity of the particulate material. The VB autometer is capable of progressively varying the magnitude of the first voltage. A measuring circuit, for measuring a second voltage, is coupled to the voltage breakdown cell. When the second voltage substantially equals a preselected reference voltage, the first voltage substantially equals the breakdown voltage of the particulate material.