CABLE DESIGN AND MANUFACTURE 



209 



Fig. 8 — Photograph of capacitance monitor electrode and servo-controller 

 console in laboratory setup. 



sides of the core will have different direct capacitances to the central 

 conductor, when the conductor is not properly centered. 



A simplified block diagram of the concentricity gauge is shown in Fig. 

 9. Data obtained with two sets of electrodes displaced 90° were recorded 

 on a strip chart recorder, with the output of the two sets of electrodes 

 being displaj^ed alternately. A satisfactory degree of centering was 

 moderately easy to maintain. 



ELECTRICAL MEASUREMENTS 



To assist in achieving the goal of matching the cable and the repeater 

 characteristics with a minimum of deviations, electrical measiu'ements 

 were made throughout the process and close tolerances were placed on 

 the electrical parameters in each stage of production. Measurements on 

 the repeater section lengths of cable were used as a final check to deter- 

 mine the extent to which all of the controls had been successful. The 

 primary standards used were calibrated by the Bureau of Standards in 

 the United States or the National Physical Laboratories in England. 

 These precision standards were used to calibrate the bridges frequently. 



The dc resistance of the central conductor was measured under con- 

 stant temperature conditions with a precision type of Wheatstone 

 bridge. The permissible range of resistance was 2.514 and 2.573 ohms 



