. The Bell System technical journal . ty ofAlpeth cable to within 35 per cent and Stalpeth to within 20 per thicknesses within ± inch are maintained. Formerly, the safe practice was to use an excess of approximately 10per cent over specified average in order to keep the thin side of eccentricsheath ^\ithin the minimum spot limit. Control from test set measure-ments eliminated the necessity of using an excess of polyethylene becausesheath of improved concentricity maintained close to the specified av-erage thickness does not vary below the specified minimum spot thick-ness. Th
. The Bell System technical journal . ty ofAlpeth cable to within 35 per cent and Stalpeth to within 20 per thicknesses within ± inch are maintained. Formerly, the safe practice was to use an excess of approximately 10per cent over specified average in order to keep the thin side of eccentricsheath ^\ithin the minimum spot limit. Control from test set measure-ments eliminated the necessity of using an excess of polyethylene becausesheath of improved concentricity maintained close to the specified av-erage thickness does not vary below the specified minimum spot thick-ness. The quality of the sheath is improved because it is of consistentlyhigh dimensional unifonnity not previously obtainable. Also, concentricsheath has better flexing characteristics since eccentric sheath concen-trates the stresses of flexing in the thin side. * Continuous Incremental Thickness Measurements of Non-Conductive CableSheath, B. M. Wojciechowski, , 33, pp. 353-368, Mar., 1954. POLYETHYLENE CABLIO SHEATH THICKNESS 563. Fig. 4—(Left) Removing test strip from end of cable; (right) performingmicrometer measurements on test strip. CALIBRATION OF THE TEST SET FOR SHEATH THICKNESS MEASUREMENTS Calibration of capacitance into thickness was difficult because thecapacitance is not a simple function of polyethylene thickness. It de-pends also on the curvature of the sheath surface, the size and shape ofthe probe, the amount of flooding and the height and shape of the cor-rugated metal. For a given probe, it depends chiefly on the thickness,the flooding and the sheath curvature. The flooding sometimes variesfrom a thin film to an that overfills the corrugations. The surfacecurvature is not unifonn because the soldering of the metal overlap ofStalpeth cable generally produces a flattened sector and the capstan atthe soldering operation results in an elliptical shape. Changes in the sur-face curvature and in the amount of flooding can be compensating orcumulative i
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
