Editing Viscometer (section)

==== Quartz crystal microbalance ====
The [[quartz crystal microbalance]] functions as a vibrational viscometer by the piezoelectric properties inherent in quartz to perform measurements of conductance spectra of liquids and thin films exposed to the surface of the crystal.<ref name=":0">{{Cite journal|last=Johannsmann|first=Diethelm|date=2008|title=Viscoelastic, mechanical, and dielectric measurements on complex samples with the quartz crystal microbalance|journal=Physical Chemistry Chemical Physics|language=en|volume=10|issue=31|pages=4516–34|doi=10.1039/b803960g|pmid=18665301|bibcode=2008PCCP...10.4516J|issn=1463-9076}}</ref> From these spectra, frequency shifts and a broadening of the peaks for the resonant and overtone frequencies of the quartz crystal are tracked and used to determine changes in mass as well as the [[viscosity]], [[shear modulus]], and other viscoelastic properties of the liquid or thin film. One benefit of using the quartz crystal microbalance to measure viscosity is the small amount of sample required for obtaining an accurate measurement. However, due to the dependence viscoelastic properties on the sample preparation techniques and thickness of the film or bulk liquid, there can be errors up to 10% in measurements in viscosity between samples.<ref name=":0" />

An interesting technique to measure the viscosity of a liquid using a quartz crystal microbalance which improves the consistency of measurements uses a drop method.<ref name=":1">{{Cite book|last1=Bai|first1=Qingsong|last2=Hu|first2=Jianguo|last3=Huang|first3=Xianhe|last4=Huang|first4=Hongyuan|title=2016 IEEE International Frequency Control Symposium (IFCS) |chapter=Using QCM for field measurement of liquid viscosities in a novel mass-sensitivity-base method |date=2016|location=New Orleans, LA, USA|publisher=IEEE|pages=1–3|doi=10.1109/FCS.2016.7546819|isbn=9781509020911|s2cid=1584926 }}</ref><ref name=":2">{{Cite journal|last1=Ash|first1=Dean C.|last2=Joyce|first2=Malcolm J.|last3=Barnes|first3=Chris|last4=Booth|first4=C. Jan|last5=Jefferies|first5=Adrian C.|date=2003|title=Viscosity measurement of industrial oils using the droplet quartz crystal microbalance|journal=Measurement Science and Technology|language=en|volume=14|issue=11|pages=1955–1962|doi=10.1088/0957-0233/14/11/013|bibcode=2003MeScT..14.1955A|s2cid=250866968 |issn=0957-0233}}</ref> Instead of creating a thin film or submerging the quartz crystal in a liquid, a single drop of the fluid of interest is dropped on the surface of the crystal. The viscosity is extracted from the shift in the frequency data using the following equation

<math>\Delta f = -f_0^{3/2}\sqrt{\frac{\eta_l \rho_l}{\pi \mu_Q \rho_Q}}</math>

where <math>f_0</math> is the resonant frequency, <math>\rho_l</math> is the density of the fluid, <math>\mu_Q</math> is the shear modulus of the quartz, and <math>\rho_Q</math> is the density of the quartz.<ref name=":2" /> An extension of this technique corrects the shift in the resonant frequency by the size of the drop deposited on the quartz crystal.<ref name=":1" />