Oscillating plate viscometry. Part 1.—Theoretical principles

Abstract

The equations of motion are derived and solved for the component parts of the oscillating plate viscometer.⁴ A linear relation √ηρ= Qδ_liq–K, is found at constant pressure, where η, ρ, are the viscosity and density of the liquid under test, δ_liq is the logarithmic decrement of the oscillations of a thin flat plate immersed in the liquid, and Q, K are apparatus constants. Both Q and K have been derived analytically, so that if desired the method may be employed without calibration using liquids of known viscosity; K is slightly pressure dependent. The derivations of Q and K involve certain approximations, but values of these can readily be computed to within 1 %; even better accuracy can be achieved using the viscometer as a comparative device.