Mumbai University > Electronics and Telecommunication > Sem3 > Electronic Instruments and Measurements

Marks: 5M

Year: June 14

Following are the applications of a Q-Meter:

• The Q meter can be used for many purposes. As the name implies, it can measure Q and is generally used to check the Q factor of inductors. As the internal tuning capacitor has an air dielectric its loss resistance is negligible compared to that of any inductor and hence the Q measured is that of the inductor.

• Unknown impedance can be measured using Q-meter, either by series or shunt substitution method. IF the impedance to be measured is small, the former is used and if its large, the latter method is used

• Characteristic impedance of a transmission line can be measured using series substitution method

• Measurement of quality factor involving comparison of inductances and capacitances

• Another use of the Q meter is to measure the value of small capacitors. The capacitor sample is resonated with a selected inductor by adjusting the source frequency and using the tuning capacitor set to a low value on its calibrated scale. The sample is then disconnected and using the same frequency as before, the tuning capacitor is reset to again obtain resonance. The difference in tuning capacitor calibration read for the two tests is equal to the capacitance of the sample. Larger values of capacitance can be read by changing frequency to obtain resonance on the second test and manipulating the resonance formula.