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small tube filling pressures

      >>Morgan wrote:
      >>Life (hours)= (Axp^4xV)/ (kxi^2)
>>where A= inside surface area of each electrode
      >>      p= filling pressure of neon
      >>      V= tube volume
      >>      i= tube current
      >>      k= emperical factor based on the coating material

        Interesting formula, Jeff. If I may apply it to a unit of glass,
say 8'- 6" (2 meters) long of 15mm clear glass with 2 Eurobrite
electrodes and 10mm fill, on a 30ma trans.
        
        The electrode shell is approx. 30mm long by 10mm in diameter
        Cir.= Pi x D
        Cir.= 3.14159 x 10mm = 31.42mm
        Area of 1 elec.= 31.42mm x 30mm =942.6 sq. mm

        The tube volume is (Pi x r^2) x 2m or 2000mm
        Inside dia. of 15mm tube is 12mm/2 =6mm
        3.14159 x 6^2 x 2000 = 226,194 cu.mm
        
        So: 
        Where A=942.6sq. mm and; (is it one elec. or both?)
              p=10mm and;
              V=226,194 cu. mm and;
              i=10ma and;
              k=???? say 100?
        
        (942.6 x 10^4 x 226,194) / (100 x 30^2) or
        (942.6 x 10,000 x 226,194) / (100 x 900) = 23,690,050 hrs.

        Hmmm! Either I should get back to the drawing board or seriously
consider extending my warranty period.   

        Any idea what units of measure are to be used for the different
variables ? (millimeters, centimeters etc.) and what would be the
range of the k factor.
        
        Also would appear that identical tubes on 30ma and 60ma
transformers, the 30ma tube would last 4 times longer than the one
running at 60ma. 

        Would be interested in a copy of those tables by Frank Montroy.

        T   
Phil Smith
Concept Neon Ltd.
(604) 270-3934
psmith@pro.net
www.pro.net