Direct-osmosis method for cleaning a semi-permeable membrane in a RO separation module, the membrane having a feed side with foulant located thereon, and an opposite permeate side. The apparatus comprises a rotatable corrugating wheel. A processor receives the images and distinguishes between markers by comparing the position and size of unidentified markers in the current image to the position and size of identified markers in preceding images. Each multiplexer circuit is further operable to receive a respective signal from either the second integrated circuit chip or an associated external terminal when the first integrated circuit chip is in test mode. The teeth have a common tooth gap bottom diameter, and a uniform angular spacing, but have different heights and different tooth forms. At the time of recording of an image, ink ejectionnon-ejection is controlled by biasing the second drive electrode to a predetermined voltage level having the same polarity as a fine particle component contained in ink and switching the first drive electrodes between a high-impedance state and a ground level in accordance with image data.