Submitted to: Federal Interagency Sedimentation Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/4/2006
Publication Date: 4/4/2006
Citation: Kleinert, D.E., Wren, D.G., Smith, C.K., Chambers, J.P. 2006. Development of an acoustic suspended sediment monitoring system. In: Proceedings of the 8th Federal Interagency Sedimentation Conference, April 2-6, 2006, Reno, Nevada. CDROM. Interpretive Summary: The acoustic measurement of suspended sediment concentration relies on specialized, expensive equipment. In the current work, a low cost system for measuring and storing acoustic backscatter data is being developed. This work will help to make acoustic field measurements much more feasible since more instruments can be deployed without fear of losing expensive equipment in harsh field environments.
Technical Abstract: Suspended sediments represent a serious worldwide pollutant which need to be monitored and ultimately controlled. Significant entrainment and transport of these sediments occur during adverse weather conditions and during relatively short time spans which make manual sampling and monitoring cumbersome, inefficient and dangerous. Toward that end, the development of a remote autonomous acoustic system to monitor suspended sediments in fluvial systems is considered. The system will transmit an arbitrary waveform via a Digital Analog Converter (DAC) and power amplifier using user defined inputs. This waveform can be any frequency up to 5 MHz. The receiver section is composed of two parts; 1) the modular preamplifier section which will incorporate the transmit/receive function, transducer impedance matching section and appropriate signal preconditioning in the form of voltage gain and 2) the Analog to Digital converter, which is a 12-bit 65 MSPS CMOS pipelined multi-stepped converter. The resulting A-D conversion is stored in the 16 MB of onboard RAM. The stored results are processed by an Analog Devices Blackfin ADSP-533 Digital Signal Processing chip. Other features of the unit include a serial port interface, a JTAG interface used in real-time emulation, a serial programming port which would allow real-time programming, a peripheral programming interface allowing easy changes to any of the control routines for the various peripherals and onboard power control and reset functions. The operation of the unit starts with a trigger from a stage height decision, either internally or externally, indicating that an event has occurred that warrants observation. The backscatter data is then collected for an amount of time depending on the determined depth. Multiple data sets are collected, processed using Fast Fourier Transforms and stored in memory at a rate of up to 3 times a second. Depending on the length of data capture, they are archived on board or sent to a host computer via serial port or wireless transfer. The unit is DC powered and may be put to sleep when there is no data to take to extend field deployments. This work has been supported by the USDA.