# unexpected magnitude of frequency shift

I am using the openQCM-Q to measure the viscosity of liquids. For some reason, the frequency shift is consistently about 39% larger than my calculations anticipated. I have double checked that I was calculating it correctly and my plots of frequency shift vs viscosity are good, they show a linear correlation that passes through the origin, they are just not the anticipated magnitudes by the 39%. I was wondering if anyone else has had a similar problem and might have found a solution?

any insight would be much appreciated!

thanks,

Rick

## Comments

it is a good result that the frequency vs dissipation experimental data shows linear correlation that passes through the origin

I'd need more information to figure out your results and check the calculation. particularly what kind of liquid is in contact with the surface of the qcm.

For example, if the liquid in contact with the quartz crystal surface can be modelled as a semi - infinite viscoelastic layer the following relations works:

Frequency variation

Dissipation variation

where

is the fundamental resonant frequency

are the piezoelectric shear strength and mass density of the quartz crystal

are the density and viscosity of the liquid

In particular, by combining the equations above we have:

no matter what kind of liquid is in contact with quartz crystal surface.

if the above hypothesis is applicable to your experiment, we can check your results together on the basis of these calculations