• A computercontrolled turbidity apparatus
    • I_t = I_0e^{-(α+τ)l}
    • We're looking for τ.
    • Aparatus for measuring turbidity as function of temperature; includes oven to place sample in. Claims 0.001/mm accuracy and 0.5% precision.
    • They measure transmitted light and assume no absorbtion; use a laser of polarized light with beam splitter.
    • Use chopper to measure ac instead of dc, claim order of magnitude better long-term stability from it.
    • Much improvement from simultaneous reference and measurement beam.
  • Simple Ratio Photometer
    • Analog instrument using photomultipliers and a mercury lamp.
    • Taking a reference while measuring (instead of before or after) allows for a less stable light source.
  • Comparison Type Nephelometer
    • Measure transmitted and scattered light with an integrating sphere each, and direct intensity, all three at once.
    • Polarized, old style (1952), not really useful.
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