A Method for Determing Logarithmic Decrements

The Bjerknes method of determining the logarithmic decrement of the secondary of two coupled circuits is critically discussed. The Author suggests a new method for determining this decrement. An additional known resistance is inserted in the secondary (or resonant) circuit instead of in the primary circuit as is the case in the Bjerknes method. An expression for the logarithmic decrement of the secondary circuit in terms of the logarithmic decrement of the primary, and known or measurable quantities, is given. The practical application of the method is described.