Variable bar display tube using insulated electrodes

Abstract

A plasma glow tube for displaying a bar of selectable length comprises an insulating enclosure filled with an ionizable gas. The enclosure may have flat opposing sides, the inside walls of which have conductive electrodes (preferably transparent) deposited thereover in a staggered pattern such that each electrode, except the end ones, is positioned between and equidistant from two opposing electrodes. The electrodes, except for the first and last electrodes which are DC coupled to the gas, are all covered with an insulating layer so that they are insulated from the gas. A potential difference, preferably in the form of a pulse, is applied between first and second end electrodes to ionize the gas therebetween and leave an inside wall charge adjacent said second electrode. A pulse is applied between the charged electrode and the next succeeding, opposite (third) electrode to ionize the gas therebetween and leave a charge on the third electrode, and so on. After the charge has been partially shifted to its desired location, i.e., over a predetermined number of electrodes, the first and second electrodes are again pulsed, creating a second charge which is in turn shifted, in synchronism with the first charge. Thereafter equally spaced third and succeeding charges are created and shifted in succession. When the first charge reaches the desired electrode according to the desired length of the bar to be displayed, it and the succeeding charges are shifted backward and forward repetitively in tandem over the next preceeding, predetermined number of electrodes at a rapid enough rate so that all groups of predetermined electrodes appear to glow continuously, whereby the entire gas from the first to the desired electrode appears to glow continuously. Isolated segment or segments of the gas can also be made to appear ionized continuously by other modes of pulsing and charge manipulation.