美制电线标准AWG与公制、英制单位对照

在以太网和xDSL接入网设计中，经常会碰到诸如24AWG、26AWG等等表示电缆直径的方法。其实AWG(American Wire Gauge)是美制电线标准的简称，AWG值是导线厚度（以英寸计）的函数。下表是AWG与公制、英制单位的对照表。其中，4/0表示0000，3/0表示000，2/0表示00，1/0表示0。例如，常用的电话线直径为26AWG，约为0.4mm。AWG外径截面积 (mm2)
电阻值 (W/km)
AWG外径截面积 (mm2)
电阻值 (W/km)
公制mm英制inch公制mm英制inch4/011.680.46107.220.17220.6430.02530.324754.33/010.400.409685.010.21230.5740.02260.258848.52/09.270.364867.430.26240.5110.02010.204789.41/08.250.324953.490.33250.440.01790.162479.617.350.289342.410.42260.4040.01590.128114326.540.257633.620.53270.3610.01420.102112835.830.229426.670.66280.320.01260.080422745.190.204321.150.84290.2870.01130.064728954.620.181916.771.06300.2540.01000.050736164.110.162013.301.33310.2260.00890.040132173.670.144310.551.68320.2030.00800.031658383.260.12858.372.11330.180.00710.025594492.910.11446.632.67340.160.00630.0201956102.590.10195.263.36350.1420.00560.01691,200112.300.09074.174.24360.1270.00500.01271,530122.050.08083.3325.31370.1140.00450.00981,377131.820.07202.6276.69380.1020.00400.00812,400141.630.06412.0758.45390.0890.00350.00622,100151.450.05711.64610.6400.0790.00310.00494,080161.290.05081.31813.5410.0710.00280.00403,685171.150.04531.02616.3420.0640.00250.00326,300181.020.04030.810721.4430.0560.00220.00255,544190.9120.03590.566726.9440.0510.00200.002010,200200.8130.03200.518933.9450.0460.00180.00169,180210.7240.02850.411642.7460.0410.00160.001316,300??由表中归纳出的AWG与英寸的关系如下：
?? AWG = A lg inch - B
??其中，A＝-19.93156857，B＝9.73724。
如哪位网友知道它们的确切关系，请告知.