u03bc and t values likely to be encountered such a table may be generated for a variety of common casing types and of a specific radius fig6 a is a graphical illustration of a typical pair of b a and b t values for a particular set u03c3 i u03bc j t k of casing parameters the values of b a and b t are calculated at a succession of points in u03c3 u03bc and t spaced at intervals sufficiently small so that the fields vary linearly between points in the table the result is a three dimensional mesh or table of the values of b a and b t for any value of u03c3 u03bc and t this is referred to as the master casing parameteres table the table need only to be calculated only once for the entire range of anticipated casing parameters and for the fixed spacing of the auxiliary receivers and chosen operating frequencies adjacent points in u03c3 u03bc and t space define an elemental rectangular volume the values of b a and b t at an arbitrary value of u03c3 u03bc and t within this elementary volume can be obtained by linear interpolation between the values on.