Lubricant contamination is often measured in the field using an optical particle counter. For oil containing wear particles or other solid contaminants, this is a great tool for providing a quantitative measure of how many particles of a given size are present in the fluid. However, because of the way these optical counters work, anything that scatters the light is counted as a particle, and it turns out that this includes lubricant additives. So, even in brand-new and perfectly clean oil, good lubricant additives can be detected as bad particles.
Wear particles, depending on their size, shape and hardness, as well as the application in which the oil is being used, can cause significant problems in machinery. Measuring the number and size of particles present in an oil can alert equipment operators to the need for fresh oil or to a potential problem within the system.