Electrostatically induced potential difference between conductive objects contained in a partially opened metal box

When a charged body exists near an opening of a partially opened metal box of an electronic apparatus, a potential difference is induced between conductive objects contained in the box. If the charged body moves, the potential difference changes and is capable of causing the breakdown of microelectronic devices in the box. However, one can rarely find a thorough study of this voltage. In this study, a potential difference induced between two metal foils in the partially opened metal box is measured without electrical connections. In some experiments, a piece of foil is grounded, whereas in others, both foils are ungrounded (floating). The measured result shows that the potential difference for a piece of foil grounded in the box is approximately 80% larger than that for both foils ungrounded. The potential difference decreases linearly by increasing the logarithm of the distance between the charged body and the front of the metal box. The result will provide a basis for a design to prevent the possible malfunction and breakdown of electronic apparatuses.