| 摘要 |
A system for determining the fractional capture efficiency of filters includes two filters having substantially the same capture efficiency connected in series. A steady, controlled flow of ultrapure water and a colloidal silica suspension is directed through both filters, with respective stages of the flow upstream of the upstream filter, between the filters and downstream of the downstream filter, directed to respective non-volatile residue monitors. Each residue monitor produces a digital output representing the non-volatile residue concentration at its respective stage. A microprocessor receives the digital outputs and generates respective residue values indicating residue concentration in parts per billion. The three residue values are used to characterize the residue by proportion of the colloidal silica suspension to other residue components, and to calculate filter capture efficiency with respect to the colloidal silica. In an alternative embodiment, a valve selectively, individually and alternatively directs each one of the flow stages to a single non-volatile residue monitor. As a further alternative, when the concentration of dissolved impurities is known to be small as compared to the colloidal silica concentration, filter efficiency can be determined using a single filter and two non-volatile residue monitors.
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