Particle Count Analysis (NAS 1638)
Both NAS 1638 & ISO 4406 focus on the methods of calculating Particle counts or a solid contamination level within the Oil Sample.
Determining ISO Cleanliness Code
Most oil analysis samples that receive particle counting are getting what is known as automatic particle counting (APC). The current calibration standard for APC is ISO 11171. When sending a sample through an APC, particles are counted either through laser or pore blockage methods. Although different laboratories may report different particle count micron levels, an example of the various reported micron levels includes those greater than 4, 6, 10, 14, 21, 38, 70 and 100 microns.