INFICON RQCM - Quartz Crystal Microbalance Research System - Manual (Page 60)

RQCM – RESEARCH QUARTZ CRYSTAL MICROBALANCE
THEORY OF OPERATION 5-8
Resistance Change vs. Wt % Glycerol
0
1000
2000
3000
4000
5000
0 20 40 60 80 100
Wt % Glycerol
Delta Resistance (ohms)
Theory
RQCM
Figure 15 Resistance Change vs. Wt % Glycerol
5.4.1 DECAY LENGTH OF SHEAR WAVE IN LIQUID
As mentioned in the section above, when an oscillating crystal is in contact with a liquid, there
will be a decrease in the resonant frequency and an increase in the motional resistance. The
decrease in the resonant frequency is caused by the additional mass of the vibrating liquid. The
increase in motional resistance is caused by the power dissipation of the shear wave that radiates
into the liquid. The decay length of the shear wave into the liquid is defined by
Equation 9
S L
L
D
L
ω ρ
η
⋅
=
2
Where:
L D
= Decay length in m
L
ρ = Density of the liquid in contact with the electrode in kg/m 3
L
η = Viscosity of the liquid in contact with the electrode in kg/m/sec