OTT ADC Acoustic Digital Current Meter Description of meter and Results of USGS testing Dan Wagner Hydrologist Arkansas Water Science Center Hydroacoustics Webinar May 24 2010 Outline ID: 772844
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OTT ADC Acoustic Digital Current Meter: Description of meter and Results of USGS testing Dan Wagner Hydrologist Arkansas Water Science Center Hydroacoustics Webinar May 24, 2010
OutlineDescription of ADCResults of USGS TestingNew USGS Firmware / enhancements
ADC HistoryReleased in USA December 2007 Testing by HIF, HAWG, and WSCs from 2008-2010New USGS Firmware currently in Beta Testing
System Components Figure courtesy of OTT
Handheld Display Figure courtesy of OTT
Handheld Display Operation Figure courtesy of OTT
Display Screen Figure courtesy of OTT
Location of Sample Volume ADC ADV
Measuring Principle Two 6 MHz acoustic transducers Large sample volume located in front of sensorLarge sample volume reduces potential signal-to- noise (SNR) issues, reduces error with flow anglesTwo sample volumesImproves data precisionInternal cross correlation calculation verifies measurement accuracy and identifies potential boundary issues 4 in 2 in Sensor head Sample volume 2 Sample volume 1 0.4 in Figure courtesy of OTT
1. Transmit – Receive - Digitize 2. Transmit – Receive - Digitize Break Cross Correlation Check for similarities Calculation of time shift D t Calculation of flow velocity 3.93 in 1.97 in 0.4 in Measuring Principle Slide courtesy of OTT
Depth Sensor Calibrate by zeroing to atmospheric pressure on site (raise out of water to calibrate) Get depth for each vertical by first lowering meter to bottom, rod offset computed automaticallyHand-held display shows target depth and actual depth for velocity measurement in vertical depending on the velocity method selected by the user. Depth sensor can be turned off with new firmware
QA/QC Figure courtesy of OTT
QA/QC checksWith new USGS firmware, a Quick QA/QC check is performed in office (similar to ADV beam check, can print results)Pre-measurement QA/QC check is logged with measurement file and appears on printout
Qreview Software-Data Download
Measurement Review
Arkansas Test Sites N
Vmean, Test Measurements Site V mean,ADV V mean,ADC % error Mud Creek 0.03 0.014 -53.3 Richland Creek 0.39 0.45 +15.4 Brush Creek 0.46 0.42 -8.7 Baron Fork 0.49 0.44 -10.2 Flint Creek nr. West Siloam Springs 0.60 0.58 -3.3 Flint Creek nr. Springtown 0.80 0.77 -3.3
Vmean, Test Measurements Site V mean,ADV V mean,ADC % error Illinois River nr. Savoy 0.84 0.90 +7.1 Bear Creek 0.85 0.84 -1.2 Middle Fork White River 1.22 1.14 -6.6 Osage Creek 1.47 1.45 -1.4 Yocum Creek 1.97 1.95 -1.0 White River nr. Fayetteville 2.04 2.05 +0.49
Percent Difference of Velocity Measured with ADC Relative to Velocity Measured with ADV
Figure courtesy of Kevin Oberg, OSW
Figure courtesy of Kevin Oberg, OSW
Figure courtesy of Kevin Oberg, OSW
Figure courtesy of Kevin Oberg, OSW
Figure courtesy of Kirk Thibideaux, HIF
ADC Pros/Cons-prior to USGS firmwarePros: Depth SensorSample volume in front of meter Rugged Construction, cablingRechargeable battery2 beams-improved performance in environments with low SNR, anglesLive velocity reading-can help with meter placementCons: Depth SensorSample volume in front of meter Rechargeable battery (?)Can’t edit erroneous stations until reviewing the measurement in QreviewLack of beam check (“bucket test”) and/or quick field QA/QC check that is logged with measurement Lack of QA/QC warnings during measurement (i.e., for 0.2/0.8 velocity discrepancies, bad correlation resulting from bad boundary conditions
Software Enhancements Enhanced quality assuranceIncluding pre-deployment quality check and field quality checkAbility to enter rated Q Expanded character limits for station name and number and addition of measurement numberComputation and recording of averaged flow anglesOn-screen warning messages, a.k.a., Measurement GuidanceProvide user with options to improve measurement resultsOption to turn off depth sensorEnhanced measurement reviewDetailed discharge and quality check reports Warning and potential quality issue logsOne-second time series data
New ADC QA/QC Warnings Figure courtesy of OTT
Questions?