Series RLC circuit at resonance behaves like a voltage magnifier.
Q-meter stands for quality factor meter whose principle of operation is series resonance.
A quality factor meter is basically a series RLC circuit.
Q-meter measures the Q-factor of a coil when the circuit is in resonance.
There are three types of connections in the Q meter.
Direct connection/ Direct measurement mode: This is used for the measurement of the various electrical properties of an unknown coil.
Qtrue = true or actual Q of the coil
R- resistance of the coil
L - self-inductance of the coil
Cd- distributed capacitance of the coil.
Series connection: This is used for the measurement of unknown low impedance.
Shunt connection: This is used for the measurement of unknown high impedance.
Series RLC Circuit:
Condition for Series resonance is,
A series RLC circuit behaves as a voltage magnifier at resonance that is the input voltage will be magnified by Q times and appears across the capacitor.
Q meter is nothing but a series RLC circuit where two voltmeters will be connected across the supply and the capacitor to measure the voltage.
Direct connection of Q meter:
R should be connected in parallel as the voltmeter is connected across the supply.
Three error sources:
- Residual inductance
- Shunt resistance(r)
- Self capacitance of the coil(Cd)
