I have noticed many discussions about the lifetime specifications of Nixies. I haven't noticed anyone quoting the manufacturer definition of lifetime - but I may have missed it. So, read on .......
"Electronic Counting circuits techniques devices ", Mullard Limited, October 1967. approx. 220 pages. Many circuits. Various authors and sources. There seem to be about eight of these books available through ABE ranging $20 to $60. Bound to be others at the usual places too. The approx 13 page chapter on numerical indicator tubes is based on material supplied by B. Butler of the Mullard Industrial Electronics division. I have included some of the text below rather than attach scans [if allowed], John Kaesehagen Australia. >From the 'numerical indicator tubes' chapter I quote this [via OCR] :- "The normal figures quoted in published data for the life of a numerical indicator tube are 5000 hours with a continuous display of one character, and 30 000 hours when sequentially changing the display from one digit to the next every 100 hours or less. The end of life for the above figures is taken to be the time when any character is unable to be covered completely, although several more thousand hours would probably have to elapse before the character became completely indecipherable." The above is contained within this section:- " LIFE PERFORMANCE The expected life performance of a numerical indicator tube depends to a greal extent on the length of time the discharge is investing any particular cathode. With any gas-discharge device, the cathode is subjected to constant ion bombardment which removes material from the cathode and deposits it elsewhere in the tube. This "sputtering" process, as it is known, is, in fact, put to good use in many cold cathode gasfllled tubes during processing. The cathode surlaces are cleaned in this manner and any sputter material thrown on the glass walls of the envelope effectively seals in any foreign matter that may affect the performance of the tube during its life. In a numerical indicator tube, however, although a clean cathode is desirable, sputter material on the envelope would impair the visibility of the display. Some sputtering is unavoidable, but since the rate of sputter is proportional to the peak current of the tube, it can be contained within limits. If one cathode is continually glowing, sputter material from that cathode is deposited on other cathode surfaces in close proximity. Although the legibility of the glowing cathode is not affected to a great extent, the cathodes on which the sputter is deposited are affected. In fact, the work function of the metal of the adjacent cathodes alters in such a way that it requires a higher current to completely cover the cathode and if this current is not available, the cathode appears patchy. This imposes a minimum permitted current level on the tube. It is possible that complete erosion of the cathode may result from bombardment, but this is unusual. If the discharge is cycled betweerr characters fairly regularly, this gives a very much improved life figure since each cathode, although receiving some sputter material, is subjected to the cleansing action of bombardment. In this case, the higher the current, the more effective the cleansing. The viewing area of the envelope is protected from sputter material by the use of a shield, or mesh, which is usually connected to the anode. >From the foregoing it is evident that the end of life of a numerical indicator tube is not abrupt, but takes the form of a gradual deterioration of a character. This is convenient, because it enables a tube which is showing signs of deterioration to be replaced before it fails completely. The normal figures quoted in published data for the life of a numerical indicator tube are 5000 hours with a continuous display of one character, and 30 000 hours when sequentially changing the display from one digit to the next every 100 hours or less. The end of life for the above figures is taken to be the time when any character is unable to be covered completely, although several more thousand hours would probably have to elapse before the character became completely indecipherable. If a tube is operated with a bulb temperature below 0"C, the mercury inside the tube condenses, resulting in a slight increase in the sputter rate. However, if the consequent shortening of life can be tolerated, an operating temperature range of -50 to +70"C can be achieved. " -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
