The SV-10 Vibro Viscometer complements the Zetasizer range of instruments and measures the dynamic viscosity of Newtonian samples. This note is to clarify what viscosity value is measured, and how it should be used in the Zetasizer software
The A&D SV-10 Vibro Viscometer is supplied by Malvern Instruments Limited to compliment the Zetasizer range of instruments to measure the dynamic viscosity of a near Newtonian sample. An overview of the SV-10 can be found in technical note MRK650 "SV-10 Vibro-viscometer (VIS5001)".
The purpose of this technical note is to clarify what viscosity value is measured by the SV-10 and how it is related to the value required to be entered in the Zetasizer software for dynamic light scattering and zeta potential measurements.
The sample's (dynamic) viscosity is required to obtain correct results for both size and zeta potential measurements for samples where the viscosity is not the same as that of the dispersant, or the viscosity of the dispersant is not known. This is usually the case when the dispersant is a mixture of salts or solvents where literature data is not available.
Viscosity Value Determined by the SV-10
The SV-10 vibro viscometer measures the product of viscosity and density i.e. SV-10 Viscosity (in mPa.s) = Dynamic Viscosity (mPa.s) x Sample Density (g/cm3)
For samples with a density of 1.00 g/cm3 (for example, pure water), the values of viscosity reported by the SV-10 are therefore dynamic viscosities.
However, for samples which do not have a density of 1.00 g/cm3, the dynamic (actual) viscosity as needed by the Zetasizer software is calculated by dividing the SV-10 viscosity by the sample density. Methods for determining the sample density are discussed in MRK650 available from the Malvern website.
The density-corrected viscosity displayed in mPa.s (milli Pascal seconds) is numerically equal to the viscosity in cP (centi poise) i.e. 1 mPa.s = 1 cP.
Care should also be taken to take note of the temperature the viscosity is measured at. The Zetasizer systems can control the temperature to that of the viscosity measured which is also displayed on the SV-10 screen.
If the size or zeta potential measurement needs to be measured at a particular temperature (i.e. 25°C) then it is important to control and measure the viscosity of the sample at this temperature (i.e. 25°C).
The following accessories are available to enable temperature control:
VIS0037 Thermostatted sample cup holder. This can be used with temperature control units that provide an external circulation of temperature controlled water
114333 Digital Temperature Control Unit. For 220V 50Hz
114343 Digital Temperature Control Unit 110V 60Hz
For information, the SV-10 does not measure the kinematic viscosity. If necessary, this can be calculated by dividing the SV-10 displayed viscosity by the density to the power of two, i.e. ƞ(SV-10) / (ƿ/ƿ) or ƞ(SV-10) / ƿi2