Underwater video camera. The camera is encased in an underwater 

 video housing. The housing was mounted to a long pole and attached to a 

 cart above the water, which allowed it to be easily relocated and removed 

 from the water when not in use. 



Instrument characteristics 



ACP. The maximum range is 2.6 m. The operating frequency is 5 MHz. 

 Nominal beam width is 3.2 deg. The pulse length is selected to 20 /isec, and 

 its repetition rate is 100 Hz. Power requirement is 24 V DC at 300 mA. The 

 output frequency, voltage, and noise are 455 kHz, 1 V peak to peak, and 

 300 mV peak to peak at maximum, respectively. The time varying gain is set 

 to 20 log(i?-0.007) + 4.54(i?-0.007) + 10 db, where R is range in meters. 

 The analog output is demodulated and then digitized by a Data Translation 

 DT2831 board. The digital range is to 4,095. 



OBS. The dynamic range for sand and turbidity are 100 to 100,000 mg/£ 

 and 0.5 to 2,000 FTU, respectively. The nonlinearity for sand is 3.5 percent 

 over to 600,000 mg/£. The power requirement is 9 to 30 V/57 mA. 

 Output span is to 3.5 V. The cutoff frequency of the output filter is 20 Hz. 

 The RMS noise at FTU is less than 100 /tV. The analog output is digitized 

 by an Onset Computer Tattletale 6. The digital range is to 4,095. 



EMCM. The full-scale range of water velocity components is -3 to 

 +3 m/sec. Analog voltages are scaled from -4 to +4 V. Long-term zero 

 drift is less than 2 cm/sec. Nonlinearity is 2 percent of reading. Absolute 

 calibration error is 2 percent of reading. Supply current is 18 mA at 6 V DC. 

 The analog output is digitized by the Onset Computer Tattletale 6. The digital 

 range is to 4,095. 



Pressure sensor. Rated and proof pressures are 20,000 and 40,000 psi. 

 The full-scale output is a nominal 5-V DC standard. Analog output is digi- 

 tized by the Onset Computer Tattletale 6. The digital range is to 4,095. 



Pore pressure sensor. The operating pressure range is 5 psi. The 

 nominal excitation range is 5 V at 6 mA. The output voltage at nominal 

 excitation is 35 mV. The zero offset is -10 to + 10 mV. The combined 

 nonlinearity and hysteresis is -0.2 to +0.2 percent BSL. Analog output is 

 digitized by the Onset Computer Tattletale 6. Digital measurement is made in 

 one of five overlapping ranges each ranging from to 4,095. 



Underwater video camera. The format of the image signal is NTSC Hi-8 

 type. Temporal resolution is 30 frames per second. 



Chapter 10 Intermittent Near-Bed Sediment Suspension 



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