A single prong, multiple signal conducting plug and plug detection circuitry is provided. Each element comprises an elongate region having a length at least twice its width and also greater than the effective dominant wavelength of light generated in the device. Each of the main capacitive sensors include at least one pair of conductive plates capable of submersion in the at least three insoluble fluids, and the geometries of the pair of conductive plates differ and are distinct, such as in distance or in width, in each of the main capacitive sensors. Good winter hardiness is made possible and the plant has been found to be relatively free of insect and disease problems during observations to date. Once the buffer is filled, a sum and standard deviation are calculated for the first n data points. The method comprises the step of performing electron beam exposure or ion beam exposure for drawing only on a diffraction grating region on which said diffraction grating is provided in correspondence with a pattern of said diffraction grating, and masking the diffraction grating region and exposing a region other than said diffraction grating region with light or X-rays.