An opto‐electronic sediment detector and its use in the chemical micro‐profiling of lakes

SUMMARY. A device for detecting (with minimum disturbance) the sediment‐water interface in lakes is described. It is based on a commercially available slotted ‘opto‐switch’ incorporating a light emitting diode and a phototransistor. The design of an audible and visual indicator is given. Possible uses are discussed and an example of chemical micro‐profiling near to the sediment with the aid of the device is reported.