Optical Liquidborne Particle Counter Operation

Abstract

Optical liquidborne particle counters are used to characterize the concentration and size distribution of solid materials that may be suspended in liquids used in cleanroom operations. The instruments are capable of counting and sizing single particles ranging in size from approximately 0.05 μm in diameter to the millimeter size range. Particles in suspensions containing up to 50,000 particles per milliliter of liquid can be sized and counted at rates to thousands per second. As is the case with any optical particle counter, operation of the liquidborne particle counter is such that data can be accumulated with both counting and sizing errors and no indication that errors may have occurred. Errors can arise either from faulty design or construction of an OPC or from incorrect operational procedures. Operation of these devices is discussed here so that many errors can be avoided. A brief description is also given of some methods other than optical response that are commonly used for counting and sizing particles in liquid suspensions.