364 



THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1954 



0.17 

 0.16 

 0.15 



[2 0.14 



I 

 o 



? 0.13 



z 



10 0.12 

 <o 



UJ 



z 



^ O.ll 



o 



I 



K 0.10 



z 



H 0.09 

 < 



<r) 0.08 

 0.07 



-20 -10 10 20 30 40 50 60 70 80 90 100 

 CAPACITANCE X 0.005 /i/CiF 



Fig. 6 — Capacitance versus thickness measurements of poljethylene plate 

 samples. 



25 measured points, 21 are contained within ±0.003 inch Hmit off an 

 average curve. Three out of four remaining points (marked "A") were 

 found to be from cable areas where application of the thermoplastic 

 cement was excessive (explanation for an extraneous position of the 

 fourth point had not been found by the time these measurements were 

 concluded). 



On the basis of over 800 measurements it has been estimated that at 

 least 75 per cent of the plotted points are within the limits of ±0.003 

 inch deviation from an average capacitance versus thickness curve, for 

 samples taken from the same cable. For samples taken from different 

 cables these deviations ranged sometimes up to ±0.005 inch. A few 

 points (less than 5 per cent) showed deviations larger than 0.01 inch. 

 With some rare exceptions, these extreme deviations indicated larger 

 than actual sheath thicknesses, and in most of the cases they were 

 associated with areas where an excess of the flooding cement was present. 



3.2 Incremental Capacitance Measurements on the Production Line 



Experimental measurements on over 500 feet of cable length were 

 performed on the production line with one of the bridge arms connected 



