An improved Iowa sediment concentration analyzer

The Iowa Sediment Concentration Measuring System (ISCMS) is an electro-optical instrument designed for measuring suspended sediment concentrations in situ. The instrument employs a small light source and sensor which responds to particles interrupting the light from the sensor. The improved model has a higher carrier frequency to eliminate the influence of particle velocity on mean measurements and to improve the high-frequency response of the system. This change in carrier frequency required that 11 circuits be redesigned. A particle generator, consisting of small partially drilled holes in a rotating disk, was used to evaluate instrument performance. The results of tests conducted with this generator showed that mean concentration measurements for particle velocities as high as 7.3 m/s were unaffected by particle velocity. Also, the -3-db upper frequency limit occurs at a particle velocity greater than 3.7 m/s.