D & A Instruments manufacture a range of field proven Optical Back Scatterance sensors for the measurement of suspended matter and turbidity in the clearest to most turbid waters in rivers, lakes and the ocean. Applications include water and wastewater monitoring, laboratory measurements, river gauging, sediment transport studies and as an OEM component in oceanographic, water quality and process control instrumentation. With the addition of a CTD sensor suite and internal data logging the OBS can be left unattended for many months to record water quality.