A light display apparatus to illuminate diffused light in a variety of chosen designs including letters, objects, numerals, images, etc. There is also provided a device for sampling of a substance from an organism on continuously or intermittently using alternating polarity method based on the application of low intensity electric fields of alternating polarity across the skin to enhance the transport of a substance from body tissues to a sampling chamber. The monitor includes a revolution sensor which sends a pulse per revolution of the main shaft of the machine to a microcomputer. The roll axis is perpendicular to the pitch and yaw axes.