Time-pulse measurement of the inductance of iron-free coils

Conclusion

The measuring accuracy and time required for the measurement of iron-free induction coils by the time-pulse method are almost entirely determined by the compensating method employed to allow for the error introduced by the active impedance of the coil under test. The method of compensation based on connecting a discretely variable resistance in series with the inductance not only enables the resistance r of the coil to be determined but also gives a more accurate measurement of the inductance. However, in this case the rapidity of action suffers, since the rate of changing the resistance Ry is limited by transient processes in the RL circuit. Compensation methods based on a change in the supply voltage E₀ of the R₀ circuit give greater rapidity. The time required to measure the inductance increases negligibly on using these methods, since noncontact switches may be used to vary the voltage E₀. The greatest rapidity of action is achieved by using the voltage in the test coil itself as the corrective agent, since in this case the rather slow-acting circuits for determining the r/R₀ ratio are unnecessary. However, with this method of compensation the accuracy of the measurements is some four times worse than in the case of a linear variation of the additional voltage.