AUTOMATIC DIGITAL Q-METER: NEW APPROACH TO THE DIGITAL MEASUREMENT OF MAGNIFICATION FACTOR.

The new procedure, presented in this paper, results in the numerical display of the Q-factor of an oscillatory circuit (or of its self-inductive element) at a relatively high resonant frequency. The procedure is based on the determination and numerical display of the ratio between the overvoltage, created by the resonance, and the high-frequency voltage injected in the oscillatory circuit. During sweeping of the frequency-modulated injection signal around the proposed resonant frequency, differentiation of the corresponding resonance curve is made; passage of the differentiated signal through the zero value is marked by an appropriate comparator circuit. The corresponding overvoltage, as well as the injected voltage, are at that moment detected and converted into the proportional dc voltages. The ratio of these voltages (which gives also the measured Q-factor) is displayed on the digital indicator, after their conversion either in two proportional frequencies or in two proportional time intervals.