Turbidimeter based on a refractometer using a charge-coupled device

Salinity and turbidity are two important seawater properties in oceanography. We have studied the use of a high resolution refractometer to measure the salinity of seawater. The requirement of a multifunctional sensor makes the turbidity measurement based on our refractometer valuable. We measure turbidity according to the attenuation of the laser beam caused by the scattering. With the configuration of our refractometer, several issues impact the laser beam attenuation measurement, while the measurement of salinity is impacted by the scattering as well. All these issues make light distribution nonsensitive sensors such as position sensitive devices unsuitable for building the refracto-turbidimeters. To overcome these issues, a charge-coupled device combined with a new location algorithm is used to measure both the refractive index and the attenuation. Several simulations and experiments are carried out to evaluate this new method. According to the results, the way to improve the resolution is discussed as well. The validation of our method is proved by comparison to the nephelometer specified by the nephelometric turbidity unit standard.