OPTICAL MICROSKOPIC : Tool oil test for solid particle to get Oil Cleanliness with the International Standard ISO CODE 4406 or NAS CLASS 1638. PREVENTIVE MAINTENANCE / ENGINEERING / OIL MONITORING requires this test equipment to monitor the solid particle under 15 microns of clearance of hydraulic and lubricating the engine components. Applications : Lubrication Gas Turbine / Steam Turbine, Hydraulic Machine, Gear Box, Oil Transformer, etc.