Particle quantifier index: a dimensionless reading from an instrument that measures how much a sample disturbs a magnetic field, which is proportional to the total mass of ferrous material whatever its particle size. Spectrometers struggle to see iron particles larger than about 5 to 10 microns, so a high PQ alongside modest spectrometric iron is the classic sign of active, severe wear producing big particles.
Iron by ICP only went to 40 ppm but the PQ index jumped to 300, there's big metal moving in that gearbox.
Also heard as
- PQI
- particle quantifier
Related terms
Elemental analysis
Spectrometric measurement of wear metals, contaminants and additive elements in oil, in parts per million.
Analytical ferrography
Microscope study of wear particles pulled from oil by a magnet, used to identify how a machine is wearing.
Glitter
Visible sparkling metal flakes in drained oil or a cut-open filter, a red flag for serious wear.
Oil analysis
Lab testing of in-service oil samples to judge oil condition, contamination and machine wear.