Q-meter

Experimental methods are applicable for a wide range of frequencies. High-frequency measurements employ commercially available dielectric constant meters, Q-meters, and so on the impedance bridge method is widely employed at low frequencies. The levels of the frequencies applied experimentally are very important for data interpretation and comparison. 

The exact number of turns will have to be determined empirically. The coil inductance can be measured with an inductance bridge or a Q-meter. 

Another useful gadget is a Q-meter for measuring coil parameters if you are going into probe building. Q-meters can also measure inductances. At the present time in the U. S., the World War II vintage Q-meter is still available in the used market. There are, of course, solid state Q-meters as well. 

FIGURE 27.12 Simplified diagram for Q-Meter series resonant measuring circuit with sample holder connected. (From Nelson, S.O., Trans. ASAE, 22, 950, 1979. With permission.)... 

Schmitt (1957) called the lead vector H transfer impedance. This may he misleading hoth because impedance is a spatial scalar, whereas H is a spatial vector and with dimension [Q/meter]. 

The pickup coil is affixed to the sample tube using a saddle-shaped configiua-tion (Figure 13). A Q-meter cannot be used to determine the quality factor of this device when it is inserted in the cavity resonator, and so Qb is determined by measuring pass bandwidth M2 at -3 dB while the coil is tuned to Q by using an external coil weakly coupled to a variable-frequency oscillator (Pescia, 1965) it follows that Qb= /Mi- Finally, because of the delicate nature of its measurement, Hi is not directly measured but rather steps are taken to ensure that it remains constant. 

The dielectric constant may be measured by a Q-Meter within the frequency range in which it operates and with a suitable sample holder [73]. The g-Meter is one of the common instruments in radio frequency measurement for determining the inductance, the capacitance, the Q of electronic components, and the resonant frequencies of circuits. The g-Meter includes a variable frequency oscillator with the output coupled to a series resonant circuit (Figure 24.12) [73]. 

---