168 



description can be found in Williams (1990). The microprocessor transmits 

 raw velocity vector information along with a time signature and pre-trans- 

 mission checksum byte for each record. 



ACP/Pressure sensor. To extend independent control of and data output 

 streams from the ACP and pressure sensor, they were controlled separately by 

 an 1802-based CDP18S601 single board computer. The electronic hardware 

 used was similar to that described by van Evra (1983), with direct computer 

 control of the timing, sampling, and conversion of the ACP and pressure sen- 

 sor signals. The coded hexadecimal machine language operational program of 

 the 601 board is contained on EPROM. Similar to the Tattletale IV, the 

 program controls serial output through an RS232 port that also serves as an 

 interface to perform system checks via PCI and an oscilloscope. 



The 601 controlled two separate A/D converter boards, one for the ACP 

 and one for the pressure sensor. The ACP signal is converted sequentially by 

 dual sample-and-hold circuits fed into the two matched A/D converters, the 

 outputs of which are connected directly to the computer board data bus. The 

 pressure electronics utilize a gated voltage-to-frequency circuit that is digitized 

 at intervals matched to the ACP timing. 



The ACP is triggered 32 times a second, and each 1 10 range-bin profile is 

 added to a RAM buffer on the 601. The summed profiles at the end of each 

 second are divided by 32 to provide the 1-sec ensemble-averaged profile. The 

 averaged profile along with a timing counter and checksum are sent out 

 serially through the output port to PCI. The 2-Hz pressure values are also 

 included in the data stream with the ACP profile values. 



Data Analysis 



Analysis and interpretation methods 



The complete description of the data obtained using the laboratory version 

 of the ARMS data collection system used at SUPERTANK includes a number 

 of analysis methods as well as different levels of analysis. It includes check- 

 ing raw data integrity, as well as converting raw data to a physically 

 descriptive format. With the data in this format it is also necessary to 

 describe the context in which the data were taken, and thus a description of 

 the wave environment and background sediment environment is needed. 

 Finally, these different components are put together and the data from the 

 different instruments are combined to obtain a picture of the water motion and 

 its effect on the motion of the sediment. 



Once data are obtained and stored, the first requirement is to check the 

 whole data file for gaps and to check each data record for missing bytes. 

 Examining each record for missing bytes is accomplished by counting the 



Chapter 9 The Ohio State University Measurements 



