Abstract: Based on the principle of optical backscatter, this study develops a multi-channel device for sediment concentration measurement using micro-sensors of optical fiber. The device has a small-size probe of only 2.5 mm in diameter and produces a very slight effect on the motion of fluid to measure. It also has the advantages of large range, high sampling frequency, and synchronous measurement of multi-channels, satisfying the requirement of most laboratory experiments. The measurement range and accuracy can be adjusted by tuning light source intensity to meet the needs of different measurements. Calibration using suspended silt with a median particle diameter of 46.5 micron shows that silt concentration of up to 150 kg/m3 can be measured. The device was successfully applied to synchronous measurement of multi-channel concentration for silt suspension in the flows of homogeneous turbulence on an oscillating grid flume.

Key words: sediment concentration, optical backscatter, optical fiber, multichannel, oscillating grid