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=== Shear rheometry ===
Shear rheometers are based on the idea of putting the material to be measured between two plates, one or both of which move in a shear direction to induce stresses and strains in the material. The testing can be done at constant strain rate, stress, or in an oscillatory fashion (a form of [[dynamic mechanical analysis]]).<ref>{{Cite journal|date=1987-01-01|title=Shear rheometry of fluids with a yield stress|url=https://www.sciencedirect.com/science/article/abs/pii/0377025787800125|journal=Journal of Non-Newtonian Fluid Mechanics|language=en|volume=23|pages=91–106|doi=10.1016/0377-0257(87)80012-5|issn=0377-0257|last1=Magnin|first1=A.|last2=Piau|first2=J.M.|bibcode=1987JNNFM..23...91M }}</ref> Shear rheometers are typically limited by edge effects where the material may leak out from between the two plates and slipping at the material/plate interface.
=== Extensional rheometry ===
Extensional rheometers, also known as extensiometers, measure viscoelastic properties by pulling a viscoelastic fluid, typically uniaxially.<ref name="sciencedirect.com">{{Cite journal|date=1978-01-01|title=Extensional Rheometers for molten polymers; a review|url=https://www.sciencedirect.com/science/article/abs/pii/0377025778850034|journal=Journal of Non-Newtonian Fluid Mechanics|language=en|volume=4|issue=1–2|pages=9–21|doi=10.1016/0377-0257(78)85003-4|issn=0377-0257|last1=Dealy|first1=J.M.|bibcode=1978JNNFM...4....9D }}</ref> Because this typically makes use of capillary forces and confines the fluid to a narrow geometry, the technique is often limited to fluids with relatively low viscosity like dilute polymer solutions or some molten polymers.<ref name="sciencedirect.com"/> Extensional rheometers are also limited by edge effects at the ends of the extensiometer and pressure differences between inside and outside the capillary.<ref name="Macosko 1994"/>
Despite the apparent limitations mentioned above, extensional rheometry can also be performed on high viscosity fluids. Although this requires the use of different instruments, these techniques and apparatuses allow for the study of the extensional viscoelastic properties of materials such as polymer melts. Three of the most common extensional rheometry instruments developed within the last 50 years are the Meissner-type rheometer, the filament stretching rheometer (FiSER), and the Sentmanat Extensional Rheometer (SER).
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