The Measurement of the Power Factor and Capacitance of a Condenser by Comparison with a Mutual Inductance

In this method a capacitance is compared with a mutual inductance in a 1000-cycle a.c. network. The secondary of the mutual inductance is in the telephone bridge circuit and carries zero current. By using a Wagner ground circuit there is complete silence in the telephone at the balance point. When used as a substitution method two nearly equal condensers can be compared with each other with an accuracy that is much greater than that of the resistances employed. The final balance is obtained by adjusting a small variable self-inductance in series with the primary of the mutual inductance. For a given capacitance and frequency the value of this self-inductance is directly proportional to the power factor of the condenser, and the scale of this inductance can be calibrated to read directly the value of the power factor. Vector diagrams are given to show the relations among the capacitance, power factor, and the inductances, and a few typical measurements are recorded.