Viscosity is a critical parameter in particle analysis of liquids and various solvents in markets such as Oil and Gas, Aerospace, Hydraulics and Process manufacturing. By definition, viscosity is resistance to flow and is greatly influenced by temperature (Synlube, n.d.). For this reason, it is generally advised that all fluids set to be analyzed have a uniform temperature. When referring to an MSDS or SDS the viscosity specification, if listed, is listed at a temperature of 40°C or 104°F. A common error is the misinterpretation of viscosity specifications to be at ambient temperatures rather than the specification on the MSDS. It is therefore recommended that the end user be aware of the published viscosity terms and the specification from the manufacturer of the sample.
Traditionally particle counters are calibrated to analyze fluids at a set flow rate. Deviation in flow rate, either faster or slower, can greatly impact count data. Higher flow rates become problematic if the sample fluid is highly viscous and the flow control system cannot maintain the set flow rate. This misalignment leads to flow errors and often requires the fluid under test to be diluted which can lead to errors in final particle concentration.