ferrography - particle analysis using precision magnets to strip iron laden and other susceptible particles from a used lube oil for study; results indicate extent of equipment wear and likelihood of imminent failure. Direct-reading ferrography uses optical sensors to measure the density of particles collected and the ratio of large particles to small (fatigue related catastrophic failure generally is characterized by generation of particles larger than 10-15 microns). Analytical ferrography employs microscopic and photographic evaluation of wear particles. The test provides in-depth analysis of particle makeup (e.g., steel, copper, bronze) and type of wear (e.g., corrosion, metal-to-metal contact). See chromatography, clay/silica gel analysis, infrared analysis, mass spectrometer, particle count, spectrographic analysis.