INFICON RQCM - Quartz Crystal Microbalance Research System - Manual (Page 66)

RQCM – RESEARCH QUARTZ CRYSTAL MICROBALANCE
THEORY OF OPERATION 5-14
mechanism for canceling out the imaginary current effectively putting the center of the crystal
back on the real axis. The true series resonant frequency of the crystal is then the point where the
conductance circle crosses the real axis. This is the frequency at which the inductive and
capacitive impedance’s in the L, R & C branch cancel out and the crystal looks like a pure
resistance of value R.
Figure 23 Admittance vs. Frequency, Magnitude and Phase of Low Q Crystal
1.6
1.4
1.2
1.0
0.0
0.6
0.4
0.2
0
90
60
30
0
-30
-60
-90
MAGNITUDE
X10 -3 SIEMENS
PHASE
DEG
MAGNITUDE
PHASE
2 KHz