Viscosity Measurements of Liquids by Capillary Viscometer with a Measuring Needle
The use of a capillary viscometer with a measuring needle as working medium providing accurate viscosity measurements of small volume of low transparent liquids is discussed. Operating principle of the viscometer is described. A working formula of the viscometer is derived proceeding from Stokes equation. Presented results of water viscosity measurements in a range of 25 - 70°C match the referenced data. Pressure distribution over the perimeter of the perpendicular section of working medium (cylindrical needle) is analyzed as a function of the needle shift from central position on a capillary axis. Self-focusing mechanism of the measurement system is demonstrated.