The MANTECH turbidity flow cell has specific optical properties which are different than the cuvettes which you would manually insert (for example the sealed standards for the 3-month calibration). The difference in optical properties between the flow cell cylinder and the cuvette can cause the relationship between actual NTU and expected NTU to be slightly non-linear. This is only applicable in the low end of the measuring range, typically < 1 NTU. To ensure the lowest detection limit possible, we use multi-line to accurately capture how the optical properties of the flow cell are different than the cuvettes.
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