In one embodiment, a Schottky diode is formed on a doped region having a thickness less than about eighteen microns. The use of this instrument permits the unattended computer control, measurement and inspection of specimens mounted to the slides. The packet header includes a format field to indicate the length of the packet header and to further specify whether the packet header includes a data payload, a subset of a type field to indicate the packet header relates to the message request transaction and a message field.