INFICON PLO-10i Phase Lock Oscillator - Manual (Page 55)

PLO-10 PHASE LOCK OSCILLATOR
THEORY OF OPERATION 8-7
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 17 Resistance Change vs. Wt % Glycerol
8.4.1 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