T.O. 33B-1-1 4-77 4.7.1.24 Measurement Of Conductivity. Absolute  values  of  conductivity  are  usually  determined  by  measuring  the  resistivity  of  a  metal  under  very  closely controlled laboratory conditions.  Conductivity is calculated as the reciprocal of resistivity as follows: C=1/R Where: C = Conductivity mhos/inch R = Resistivity ohm.inch Conductivity can be converted to % IACS units as described in section 4.2.2.1.1.3 4.7.1.25 Field Measurement Of Conductivity. For  determination  of  electrical  conductivity  under  production  and  field  conditions,  eddy  current  instrumentation  is employed.    The  eddy  current  instruments  are  calibrated  against  standards  of  known  conductivity.    When  available, instruments designed specifically for measurement of conductivity are used.  These instruments measure conductivity directly in % IACS. Table 4-7.  Electrical Conductivity Ranges for Aluminum Alloys Electrical Conductivity (%IACS) Alloy and Temper Minimum Maximum 1100 (All tempers) 57.0 62.0 2041-0 48-5 51.5 2013-T3XX 31.5 35.0 2041-T4XX 31.5 35.0 2013-T6XX 37.0 41.5 2024-0 45.5 50.0 2024-T3XX 28.0 33.0 2024-T4XX 28.5 32.5 2024-T6XX 35.0 41.0 2024-T8XX 36.00 42.5 2219-0 43.0 46.0 2219T3XX 27.0 31.0 2219-T62X 31.0 35.5 2219-T8XX 31.0 35.5 3003-0 44.5 50.0 6061-0 47.0 51.0 6061-T4XX 35.5 41.5 6061-T6XX 40.0 45.0 7075-0 44.0 48.0 7075-T6XX 30.0 35.0 7075-T73X 38.0 42.5 7075-T76X 36.0 39.0 7079-0 44.0 47.0 7079-T6XX 30.0 35.0 7079-T6XX 30.0 35.0 7178-0 43.0 47.0 7178-T6XX 29.0 34.0 7178-T76 35.0 39.0