Nixie Tube - Applications and Lifetime

Applications and Lifetime

Nixies were used as numeric displays in early digital voltmeters, multimeters, frequency counters and many other types of technical equipment. They also appeared in costly digital time displays used in research and military establishments, and in many early electronic desktop calculators, including the first: the Sumlock-Comptometer ANITA Mk VII of 1961 and even the first electronic telephone switchboards. Later alphanumeric versions in fourteen segment display format found use in airport arrival/departure signs and stock ticker displays. Some elevators used Nixies to display floor numbers.

Average longevity of Nixie tubes varied from about 5,000 hours for the earliest types, to as high as 200,000 hours or more for some of the last types to be introduced. There is no formal definition as to what constitutes "end of life" for Nixies, mechanical failure excepted. Some sources (Weston 1968, p. 340) suggest that 50% reduction in emitted light would not be acceptable; however cathode poisoning resulting in incomplete digit display, while generally not preventing the tube from being used, may also be considered unacceptable. Nixie tubes are susceptible to multiple failure modes, including

• simple breakage,
• cracks and hermetic seal leaks allowing the atmosphere to enter,
• cathode poisoning preventing part or all of one or more characters from illuminating,
• increased striking voltage causing flicker or failure to light,
• sputtering of electrode metal onto the glass envelope blocking the cathodes from view,
• internal open or short circuits which may be due to physical abuse or sputtering.

Driving Nixies outside of their specified electrical parameters will accelerate their demise, especially excess current, which increases sputtering of the electrodes. A few extreme examples of sputtering have even resulted in complete disintegration of Nixie-tube cathodes.

As testament to their longevity, and that of the equipment which used them, in 2006 several suppliers still provide common Nixie-tube types as service-replacement parts, new in original packaging. Equipment with Nixie-tube displays in excellent working condition is still plentiful, though much of it has been in frequent use for 30–40 years or more. Such items can easily be found as surplus and obtained at very little expense. In the former Soviet Union, Nixies were still being manufactured in volume in the 1980s, so Russian and Eastern European Nixies are still available.

One advantage of the Nixie tube is that its cathodes are typographically designed, shaped for legibility. In most types, they are not placed in numerical sequence from back to front, but arranged so that cathodes in front of the one that is lit obscure it minimally. The digit sequence is rarely given; one arrangement is 6 7 5 8 4 3 9 2 0 1 from front (6) to back (1).