Question

In a Q Meter, the values of tuning capacitor are C3 and C4 for resonant frequencies f3 and 2f4 respectively. The value of distributed capacitance is?

(a) \(\frac{C_3-C_4}{2}\)

(b) \(\frac{C_3-2C_4}{3}\)

(c) \(\frac{C_3-4C_4}{3}\)

(d) \(\frac{C_3-3C_4}{2}\)

The question was asked in an online quiz.

I need to ask this question from Advanced Problems on Q Meter topic in division Electronic Instruments of Electrical Measurements

Answer 1

Correct option is (c) \(\frac{C_3-4C_4}{3}\)

For explanation I would say: QX = \(\frac{R_P}{X_P}  = \frac{(C_4 – C_3)Q_3 Q_4}{Q_3 C_3 – Q_4 C_4}\)

The main error in the measurement of Q is due to the distribution. To check for this, the Q value is measured at two frequencies f1 and 2f2. It should be same, if not then, \(\frac{C_3-4C_4}{3}\).