The purpose of this standard is to present test methods useful in the design, analysis, and operation of magnetic cores in many types of applications in electronics and related industries. Most of the test methods described include specific parameter ranges, instrument accuracies, core sizes, etc., which may be used in the specification of magnetic cores for industrial and military applications. Other sections of the standard describe more generalized test procedures, which are included more for the benefit of the R and D engineer and university student. This standard has been updated to include core materials, test methods, and information on measuring instruments. Information from two discontinued standards is now included. The old standards were IEEE Std 106-1972, Standard Test Procedure for Toroidal Magnetic Amplifier Cores and IEEE Std 164-1962, Methods of Testing Bobbin Cores. SI units are used throughout this standard; equivalent CGS and English units are included in some definitions. Whenever possible, all definitions and symbols are in accordance with those of the International Electrotechnical Commission (IEC).