The combination of fine and coarse wear metals is a more true indicator of current unit condition then fine metals determined by ICP, ICP being the most commonly used method for oil analysis. ICP measures particles up to about 7 or 8 microns, within the size range for normal rubbing wear. Unfortunately, particles that indicate initial problems are larger then this and they are not aspirated into the plasma, that is, they're not seen.
PQ Index is a unit-less index of the effect that the magnetic particles in a sample have on a magnetic field. If the iron content by plasma and the PQI are approximately equal then the ICP number is representative and particles are most likely normal rubbing wear. If the PQI is larger than the ICP number it suggests that something beyond normal rubbing wear is occuring and exception tests are needed. Similar correlations can be seen between ICP and x-ray fluoresence. PQI is excellent for problematic trends once a problem has been identified.
PQ Index is a unit-less index of the effect that the magnetic particles in a sample have on a magnetic field. If the iron content by plasma and the PQI are approximately equal then the ICP number is representative and particles are most likely normal rubbing wear. If the PQI is larger than the ICP number it suggests that something beyond normal rubbing wear is occuring and exception tests are needed. Similar correlations can be seen between ICP and x-ray fluoresence. PQI is excellent for problematic trends once a problem has been identified.