Probe colorimeter Model PC950 measures transmittance, absorbance or concentration. It can be used manually or with any automation package; it can be customized for a specific application by selecting a fiber optic length and drop-in filter from 420 nm to 950 nm. Features include interchangeable probe tips for various path lengths, immersions depths, and materials; analog output for use with titrators or recorders; serial computer interface for data collection; and a small footprint.