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Abstract

An automatic dilution system and method provides optimal dilution factor DF for a sample suspension containing particles mixed with a diluent. A diluent flows into a mixing chamber, and the sample is injected into the chamber. A sensor, such as a single particle optical sensor (SPOS), measures the value of a particular characteristic, which characteristic R.sub.max (0) is the initial rate of increase of a quantity related to particle concentration. A CPU/Controller calculates from R.sub.max (0) the optimal value of DF, and develops a control signal which adjusts the flow of the sample to provide the optimal value of DF. In a first embodiment, all of the diluted sample passes through the sensor. In a second embodiment, only a portion of the sample is directed through the sensor to shorten the time to reach equilibrium. The time to reach equilibrium is further reduced in a third embodiment in which the mixing means is a static mixer, having relatively small volume, inserted in series with a diluent flow tube. The sample is injected into the flow tube upstream of the mixer. Larger dilution factors are obtainable in a fourth embodiment in which the sample is first prediluted in a mixing chamber and then further diluted in a second mixing chamber. A fifth embodiment also predilutes the sample, but to shorten the time to reach equilibrium, uses a static mixer for the second dilution stage. In all embodiments, the diluted fluid may be fed to one of two branches, one having an SPOS and the other having a sensor using the light scattering principle.

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First Claim