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SonTek FlowTracker ® Basics of Operation

SonTek FlowTracker ® Basics of Operation. AN introduction to discharge measurements with a flowtracker GEOTech Environmental Equipment training center Denver, Colorado April 23 rd -25 th , 2013. FlowTracker Handheld ADV ®. Presentation Outline History of the FlowTracker

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SonTek FlowTracker ® Basics of Operation

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  1. SonTek FlowTracker®Basics of Operation AN introduction to discharge measurements with a flowtracker GEOTech Environmental Equipment training center Denver, Colorado April 23rd-25th, 2013

  2. FlowTracker Handheld ADV® Presentation Outline History of the FlowTracker Basic FlowTracker Operating Principles Firmware Features Overview Discharge Uncertainty

  3. History of the FlowTracker A direct descendant of the SonTek ADV® - invented in 1993 and used for hydraulic research in laboratories ADVs feature: Extremely high velocity precision based on pulse-coherent Doppler processing Full 3D velocity measurement 25 Hz sampling 0.25 cc sampling volume remote from instrument 4 (manual) velocity range settings Outstanding shallow water and low- velocity capability 1000+ systems in laboratory use today

  4. History of the FlowTracker Low power CMOS-based electronics platform (late ’90s) provided mechanism for compact packaging and battery operation AutoVelocity processing (invented in 2000) eliminated need for separate velocity range scales – facilitated adaptation for field use Market demand to make a tool for discharge measurement in shallow streams

  5. History of the FlowTracker Assigned as a USGS ITASS project to adapt ADV for use as a discharge measurement instrument from wading rods Some funding and cooperation from USGS Indiana (Scott Morlock) and Maryland Office (Gary Fisher) FlowTracker prototype being tested against Price AA - ~2000 Traditional ADV attached to wading rod as proof of concept Mention of the USGS does not constitute endorsement

  6. History of the FlowTracker History of upgrades and improvements: First production release (2001) High sensitivity receiver improvements (2002) 3 m probe cable option (2003) Deluxe two-piece wading rod and case (2005) Software v. 2.3 (2009) Firmware v 3.9 (2012)

  7. Basic Operating Principles ADVs are classified as Bi-static Doppler Current Meters • Central acoustic transmitter • 2 or 3 acoustic receivers • For 2D or 3D probes • Remote sampling volume • 10 cm from probe tip • 2D or 3D velocity • Full resolution of flow direction Acoustic transmitter Acoustic Receiver 2 Acoustic Receiver 1 Sampling Volume 6mm dia by 9mm height Sampling volume is fixed at 10 cm from transmitter

  8. ADV Doppler Processing • Pulse coherent processing • Best performance of any Doppler technique • Fast response time • Wide velocity range • Automatic velocity range • Adapts operation based on flow speeds • Excellent performance for flows to (4.5 m/s / 15 ft/s) • Unbeatable low flow performance • Flows less than (1 cm/s / 0.03 ft/s) • Accuracy 1% of measured velocity in 1 second

  9. FlowTracker Doppler Calibration • Velocity Depends on 3 Factors • Measured Doppler shift • Fundamental to design of Doppler processing algorithms • Never changes • Probe geometry • Factory calibration for each probe • Calibration can only change with physical damage • Diagnostic software (ADVCheck/Beam Check) easily verifies probe integrity • Sound speed • Internal temperature sensor for automatic compensation • User input salinity for salt or brackish water applications

  10. Basic Operating Principles • Pulse coherent processing • Transmit 2 pulses separated by time TLAG • Measure phase of return signal • Phase change divided by TLAG gives Doppler shift • Maximum velocity determined by TLAG • Shorter TLAG gives higher maximum velocities • Velocity noise level changes with TLAG • Longer TLAG gives lower noise levels • Adjust TLAG to give sufficient maximum velocity and lowest noise level

  11. Basic Operating Principles • Traditional ADV velocity range • User selects fixed velocity range to set TLAG • Requires knowledge of flow conditions to optimize performance • Automatic velocity range • Uses multiple pulse pairs with different TLAG settings • Based on results from one TLAG the algorithm determines if the next TLAG can be used without error • Uses the longest possible TLAG for given flow conditions, giving the lowest possible noise in velocity data • Maximum velocity is 4.5 m/s • Optimizes performance from less than 0.1 cm/s to 4.5 m/s

  12. Handheld controller AA Battery power Readily fixes to top-setting wading rods 2m (3m optional) probe cable 2D ADV probe (3D optional) Adaptation of ADV into FlowTracker product for discharge applications

  13. System Configuration • Handheld controller • Custom keypad • LCD display • Batteries (8 AA) • 4 Mb Data recorder • Complete data collection and discharge software LCD Screen Keypad External Power/Communication Connector Probe Cable FlowTracker Probe Three probe types: 2D side looking 2D/3D side looking 3D down looking

  14. Battery Requirements • Operates from 8 AA batteries • Alkaline, NiMH or NiCad • Standard rechargeable batteries can be used (user supplied or available from SonTek) • Typical battery life • Alkaline: 25 hours continuous operation • NiMH: 15 hours continuous operation • NiCad: 7 hours continuous operation • Monitoring battery capacity • Access battery voltage from keypad interface • Shows estimated remaining capacity for all battery types

  15. System Specifications • Probe configuration • 2D side looking standard • 2D/3D side looking and 3D down looking optional • Additional sensor • Temperature (±0.1° C / ±0.2° F) • Environmental • Operating temperature (-20° to 50° C / 0° to 120° F) • Storage temperature (-20° to 50° C / 0° to 120° F) • Data Quality Annunciation • Acoustic signal strength as SNR (signal to noise ratio)

  16. Case Study --Tow Carriage Testing • Velocity offset: (0.15 cm/s / 0.005 ft/s) • Performance exceeds 1% accuracy specification • Total of 71 tow carriage runs • Flow angles to ±40° • Best fit slope: 0.994*Cart speed

  17. Typical Field Velocity Data Raw Velocity Data • Sample field data • Mean velocity (45.7 cm/s / 1.50 ft/s) • Standard deviation of 1 second data (3.7 cm/s / 0.12 ft/s) – about 8% of mean velocity • Fluctuations are real variations in velocity • Standard error of 40 second average (0.6 cm/s / 0.02 ft/s)

  18. Averaging Time • FlowTracker burst sampling • Collects fixed length record of velocity at each station • User specified averaging time from 10 to 1000 seconds • Recorded data includes raw 1 second velocity, mean velocity, temperature, and extensive quality control data • Specifying averaging time • Function of the environment • FlowTracker provides standard error data in real time to determine the accurate of mean velocity data

  19. Basic Operating Principles • Menu driven interface for discharge measurement • Specify setup parameters • Perform system diagnostics • Data collection run • “Set” keys to specify station location, water depth, measurement method, etc. • Measure to start data collection • Quality control data shown with each measurement (measurements can be repeated if desired) • Next and Previous Station keys to scroll through completed station data

  20. Basic Operating Principles FlowTracker Handheld-ADV technique when used with a wading Rod and tag line Wading rod must be held perpendicular to tag line FlowTracker reports true angle of flow – no estimation required

  21. Firmware Features Midsection Method (ISO) Mid-Section Method

  22. Firmware Features Mean-Section Method

  23. Firmware Features 0.6 0.2/0.8 0.2/0.6/0.8 Arrows denote ADV probe positions on wading rod

  24. Firmware Features Kreps 2 5-point Multipoint Arrows denote ADV probe positions on wading rod

  25. Velocity Methods • Equation: how stations are combined for discharge • Method: how mean station velocity is determined • Supported methods: 16 total • Displayed methods • Can remove those that will never be used • Special cases • Method NONE • Internal islands • No measurement possible, use adjacent stations • Method INPUT V • No measurement possible, user input velocity • Method MULTI PT • Any number of measurements at any locations • Integrated mean velocity

  26. Velocity Methods

  27. Smart QC What is the goal? Best possible discharge measurement What is needed to do this? Verify instrument operation Evaluate all data used for discharge calculation Automatic warnings for a variety of QC data How well did it work? Discharge uncertainty

  28. Smart QC Is the FlowTracker working properly? Auto QC Test Run at the start of every measurement. Place the probe in moving water, well away from any underwater obstacles Takes <30 seconds, data analyzed automatically Automated version of BeamCheck PC software

  29. Smart QC Four Test Parameters Noise level SNR • Peak location • Peak shape

  30. Smart QC Why run BeamCheck from a PC if you do an Auto QC with each measurement? Running BeamCheck manually is one of the best ways to learn about the FlowTracker BeamCheck allows subjective evaluation, particularly valuable for the peak shape criteria Experienced users can use the BeamCheck in the software to achieve the same results as the FlowTracker Auto QC plots Beam Check is found in SonUtils4

  31. Smart QC Evaluates all data used for discharge calculation Data entry Location Consistent spacing, stations entered in order Depth No radical changes in depth Measurement practices %Q Is any one section greater than 10% of total discharge? Flow Angle Is flow angle > 20°? May be real at some measurement sites

  32. Smart QC SNR (Signal-to-Noise Ratio) Function of how much suspended material is in the water Must be greater than 4 dB for reliable operation Both beams should be roughly the same (<10dB difference) Most stations in a cross section should be about the same (<10 dB different from mean SNR for all stations) Standard deviation of SNR > 5 dB Spikes All acoustic systems will see some spikes in velocity data These are automatically filtered out Large numbers of spikes (> 10% of samples) is a problem Aerated water Interference from submerged object

  33. Smart QC σV : Standard error of velocity Measures variation in velocity during the averaging period Varies with the environment Higher in high velocity or highly turbulent environment SmartQC automatically adjusts criteria to the environment σV threshold: largest of following 3 values Fixed value (0.01 m/s / 0.03 ft/s) Mean of all stations Percentage of velocity Unusually high σV could be Aerated water Interference from underwater obstacle Real for localized turbulence

  34. Smart QC QC data reviewed and warnings issued At the end of each measurement When End Section pressed (all measurements reviewed) All criteria can be modified or disabled Data entry errors Location Station spacing changes dramatically Station location is out of order Depth Large depth change compared to adjacent stations Boundary QC Warning before data collection if FAIR or POOR Reposition probe and try again

  35. Smart QC Boundary QC Acoustic interference from underwater obstacles If possible, FlowTracker adapts operation to avoid interference If a warning given, re-position probe and try again

  36. Smart QC Smart QC Summary For most warnings Evaluate probe location, consider moving probe Repeat measurement If problem persists Check probe operation (Auto QC, BeamCheck) Maybe there is not a problem Higher turbulence High measurement angle Aerated water Locally high sediment load

  37. Auto QC Test • Auto QC Test = BeamCheck In Firmware • Prompted at the start of every file • Takes <30 seconds • Can be run at any other time, open data file or not • Procedure • Put probe in moving water and press start • Automatic Analysis • Noise, SNR, peak shape, peak level, • What to do if warnings? • Try again, possibly different probe location • Run BeamCheck on PC

  38. QC Menu • The QC menu is active essentially anytime during a measurement • Supplemental data • QC settings • Discharge settings • Change averaging time • Raw velocity display • Auto QC test

  39. Setting QC Criteria • Setup Parameters Menu • QC Settings Menu (Option 4) • Discharge Settings Menu (Option 5) • Also accessible from QC Menu • Set any value to 0 to disable • QC Settings • SNR Threshold (dB) • σV Threshold (m/s or ft/s) • Spike Threshold (%) • Discharge Settings • Max Section Discharge (%) • Max Depth Change (% of comparison depth value) • Max Location Change (% change in spacing) • Max Velocity Angle (°)

  40. Additional Firmware Features • Data export • BeamCheck • Recorder download International language support Windows 2000/XP/Vista compatibility

  41. Software: Data Export • HTML discharge report • Open / view multiple files • Batch processing options • Modifications to DIS file for new features and better integration with databases • Column headers (SUM, DIS)

  42. Discharge Report: Page 1-2

  43. Discharge Report: Page 1-3 HTML-based reporting Fully customizable Easily translates to 7 different languages

  44. Discharge Uncertainty Background Two Uncertainty Calculations ISO Uncertainty Calculation Statistical Uncertainty Calculation Why 2 Calculations? Comparison of Results Displaying Uncertainty Results

  45. Discharge Uncertainty What is uncertainty? How accurate is the discharge measurement Most agencies record a subjective measurement quality This provides a quantitative measure Why does uncertainty matter? Data are used for other analysis such as Stage/Discharge or Velocity Index ratings. Uncertainty propagates through these ratings.

  46. Discharge Uncertainty ISO Standard 748 International standard for discharge measurement procedures Includes a discharge uncertainty calculation Estimated uncertainty for all measured variables (depth, width, velocity) Other sources of uncertainty Limited number of stations across the river Velocity at limited number of depths at each station Above values are based on extensive studies of many different rivers Well documented formula using readily available data Similar method and results to Sauer and Meyer (USGS)

  47. Discharge Uncertainty Statistical Uncertainty Calculation: Developed by researchers at the U.S. Geological Survey Tim Cohn, Julie Kiang, and Robert Mason New technique, limited publications and field experience Also called “Interpolated Variance Estimated (IVE) method Fundamentally Different Approach: ISO: Physical properties of the measurement and calculation Statistical: Use adjacent measurements to estimate uncertainty

  48. Discharge Uncertainty Statistical Uncertainty Calculation Discharge calculation assumes linear change in depth/velocity between stations Estimate data at each vertical by interpolating adjacent data Uncertainty is measured value minus estimated value

  49. Discharge Uncertainty 24 Measurements Discharge 0.004 to 9 m3/s Velocity 0.01 to 0.5 m/s ISO 2.4 to 8.4% (all files) 2.4 to 4.3% (removing 1 file) Statistical 2.1 to 19% (all files) 2.1 to 15.2% (removing 1 file) ISO Uncertainty Statistical Uncertainty (%)

  50. Discharge Uncertainty Why 2 Different Calculations? ISO calculation International standard, well documented Critical parts from statistical averages from many different rivers Not responsive to varying data from a specific site Statistical method Appears very effective Responds to conditions and variations in data Limited publication and field experience

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