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SonTek FlowTracker® Basics of Operation

AN INTRODUCTION TO DISCHARGE MEASUREMENTS WITH A FLOWTRACKER

GEOTECH ENVIRONMENTAL EQUIPMENT TRAINING CENTER

DENVER, COLORADOAPRIL 23RD-25TH, 2013

FlowTracker Handheld ADV®

Presentation Outline

1. History of the FlowTracker

2. Basic FlowTracker Operating Principles

3. Firmware Features Overview

4. Discharge Uncertainty

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 processingFull 3D velocity measurement25 Hz sampling0.25 cc sampling volume remote from instrument4 (manual) velocity range settingsOutstanding shallow water and low- velocity capability

1000+ systems in laboratory use today

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

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)

Mention of the USGS does not constitute endorsement

Traditional ADV attached to wading rod as proof of concept

FlowTracker prototype being

tested against Price AA - ~2000

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)

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

Sampling Volume6mm dia

by 9mm height

Acoustic transmitter

AcousticReceiver 2

AcousticReceiver 1

Sampling volume is fixed at 10 cm from transmitter

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

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

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

T = 0Tran sm it P u lse 1

T = TR ece iv e P u lse 1

S

T = TTran sm it P u lse 2

L A G

T = T + TR ece iv e P u lse 2

L A G S

P h ase 1

P h ase 2

V

S in g le Ta rg e tVe lo c ity V

M easu red V ~ ( - ) / T 2 1 L A G

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

Adaptation of ADV into FlowTracker product for discharge applications

2D ADV probe (3D optional)

2m (3m optional) probe cable

Readily fixes to top-setting wading rods

Handheld controller

AA Battery power

System Configuration

• Handheld controller •Custom keypad

•LCD display

•Batteries (8 AA)

•4 Mb Data recorder

•Complete data collection and discharge software

Probe Cable

FlowTracker Probe

External Power/Communication

Connector

Keypad

LCD Screen

Three probe types: 2D side looking 2D/3D side looking 3D down looking

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

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)

Case Study --Tow Carriage Testing

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Cart speed (ft/s)

Flow

Trac

ker S

peed

(ft/s

)

FlowTracker Tow Carriage Testing January 2001

• Total of 71 tow carriage runs• Flow angles to ±40°

• Best fit slope: 0.994*Cart speed

• Velocity offset: (0.15 cm/s / 0.005 ft/s)

• Performance exceeds 1% accuracy specification

Typical Field 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)

0 5 10 15 20 25 30 35 400

0.5

1

1.5

2

2.5

3

Time (seconds)

Flow

Trac

ker V

eloc

ity (

ft/s)

FlowTracker Field Data - Raw Velocity Data

Raw Velocity Data

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

Basic Operating Principles

1 32

0 -.

7 98

4 65

EN TER

SetD epth

M easure

SetLocation

G H I

PQ R S

ABC

JKL

TU V

D EF

M N O

W XYZ

N extStation

PreviousStation

C orr.Factor

Abort

English Keypad

D elete

SetVelocity

Set M eas D epth

EndSection

M ethod+

LEW /R EW

C alculateD isch.

M ethod-

Set IceD epth

Q CM enu

Five Colors Black W hite Grey (50% ) Yellow (Pantone Yellow CVC - 100% yellow in CMYK) Blue (PMS 2935 Coated)

Fonts Num bers Keys ( 1234567890 . - ): W hite 20 Point Arial Alphabet on keys (A-Z): W hite Arial 8 Point ENTER: W hite 9 Point Arial All yellow text: Yellow 9 Point Arial

• 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

Basic Operating Principles

FlowTracker Handheld-ADV technique when used with a wading Rod and tag line

S am p lin g Vo lu m e

Y

XP ro b e

C o o rd in a te S y stem

G rad u a ted Tag L in e

P rim ary F lo wD irec tio n

M o u n tin gP in

FlowTracker reports true angle of flow – no estimation required

Wading rod must be held perpendicular to tag line

Firmware Features

Midsection Method (ISO)

L o c 0 L o c 1

1VelL o cVe l

2

2

L o cVe l

3

3

L o cVe l

4

4

L o cVe l

5

5

L o cVe l

6

6

L o cVe l

7

7

L o cVe l

8

8

L o cVe l

9

9

L o cVe l

1 0

1 0

L o cVe l

11

11

L o c 1 2

D ep 1 D ep 2 D ep 3 D ep 4 D ep 5 D ep 6 D ep 7 D ep 8 D ep 9 D ep 1 0 D ep 11

A rea 1

A rea 2

A rea 3 A rea 4A rea 5

A rea 6 A rea 7 A rea 8A rea 9

A rea 1 0

A rea 11

O p en W a te r C a lcu la tio n s S ta tio n W id th = W = (L o c - L o c )/2 S ta tio n A rea = A rea = W * D ep S ta tio n Ve lo c ity = Ve l S ta tio n D isch a rg e = Q = A rea * Ve l

To ta l D isch a rg e = S u m ( Q )

i i+ 1 i-1

i i i

i

i i i

i

W 1 W 2 W 3 W 4 W 5 W 6 W 7 W 8 W 9 W 1 0 W 11

D isch a rge M ea su rem en t - M id S ectio n E q u atio n

W 1 2

D ep 1 2

E d g e C a lcu la tio n s (S ta rtin g , E n d in g , In te rn a l Is lan d ) i = ed g e s ta tio n (L o c , D ep ) j = ad jacen t s ta tio n w ith v e lo c ity (L o c , D ep , Ve l ) E d g e W id th = W = (L o c - L o c )/2 E d g e A rea = A rea = W * D ep E d g e C o rrec tio n F ac to r = C F E d g e Ve lo c ity = Ve l = C F * Ve l E d g e D isch a rg e = Q = A rea * Ve l

i i

j j j

i j i

i i i

i

i i j

i i i

A rea 1 2

W 0

Mid-Section Method

Firmware Features

Mean-Section Method

L o c 0 L o c 1

1VelL o cVe l

2

2

L o cVel

3

3

L o cVel

4

4

L o cVel

5

5

L o cVel

6

6

L o cVel

7

7

L o cVel

8

8

L o cVel

9

9

L o cVel

1 0

1 0

L o cVel

11

11

L o c 1 2

D ep 1 D ep 2 D ep 3 D ep 4 D ep 5 D ep 6 D ep 7 D ep 8 D ep 9 D ep 1 0 D ep 11

A rea 1

A rea 2

A rea 3

A rea 4 A rea 5A rea 6

A rea 7 A rea 8 A rea 9A rea 1 0

A rea 11

O p en W ate r C a lcu la tio n s S ta tio n W id th = W = L o c - L o c S ta tio n A rea = A rea = W * (D ep + D ep ) / 2 M ean S ta tio n Ve lo c ity = M ean V = (Ve l + Ve l ) / 2 S ta tio n D isch a rg e = Q = A rea * M ean V

To ta l D isch a rg e = S u m ( Q )

i i i-1

i

i i i-1

i

i i-1

i

i i

i

W 1 W 2 W 3 W 4 W 5 W 6 W 7 W 8 W 9 W 1 0 W 11

D isch a rge M ea su rem en t - M ean S ectio n E q u atio n

W 1 2

D ep 1 2

E d g e C a lcu la tio n s S ta rtin g ed g e , seco n d ed g e o f in te rn a l is lan d Q = W = A rea = 0 .0 E n d in g ed g e , firs t ed g e o f in te rn a l is lan d i = ed g e s ta tio n (L o c , D ep ) E d g e W id th = W = L o c - L o c E d g e A rea = A rea = W * (D ep + D ep ) / 2 E d g e C o rrec tio n F ac to r = C F E d g e Ve lo c ity = Ve l = C F * Ve l M ean E d g e Ve lo c ity = M ean V = (Ve l + Ve l ) / 2 E d g e D isch a rg e = Q = A rea * Ve l

0 0 0

i i

i i i-1

i i i i-1

i

i i i-1

i i i-1

i i i

A rea 1 2

Firmware Features

0.2/0.8 0.2/0.6/0.80.6

Arrows denote ADV probe positions on wading rod

Firmware Features

Kreps 2 Multipoint5-point

Arrows denote ADV probe positions on wading rod

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

Velocity MethodsMethod Measurement Locations Mean Velocity Equation

0.6 0.6 * depth Vmean = V0.6

0.2/0.80.8/0.2

0.2 / 0.8 * depth Vmean = (V0.2 + V0.8) / 2

.2/.6/.8

.8/.6/.20.2 / 0.6 / 0.8 * depth Vmean = (V0.2 + 2*V0.6 + V0.8) / 4

Ice 0.6 0.6 * effective depth Vmean = 0.92*V0.6

Ice 0.5 0.5 * effective depth Vmean = 0.89*V0.5

Ice 2/8Ice 8/2

0.2 / 0.8 * effective depth Vmean = (V0.2 + V0.8) / 2

Kreps 2+Kreps 2-

0.0 (near surface)0.62 * depth

Vmean = 0.31*V0.0 + 0.634*V0.62

5 Point+5 Point-

0.0 (near surface)0.2 / 0.6 / 0.8 * depth1.0 (near bottom)

Vmean = (V0.0 + 3*V0.2 + 3*V0.6 + 2*V0.8+ V1.0) / 10

Multi Pt Any number of points at user specified depths

Integrated velocity average

Smart QC

What is the goal?Best possible discharge measurement

What is needed to do this?Verify instrument operationEvaluate all data used for discharge calculation

• Automatic warnings for a variety of QC data

How well did it work?• Discharge uncertainty

Smart QC

Is the FlowTracker working properly?

Auto QC TestRun at the start of every measurement.Place the probe in moving water, well away from any

underwater obstaclesTakes <30 seconds, data analyzed automaticallyAutomated version of BeamCheck PC software

Smart QC

Four Test Parameters

• Noise level• SNR

• Peak location• Peak shape

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

Smart QCEvaluates 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

Smart QC

SNR (Signal-to-Noise Ratio)

Function of how much suspended material is in the waterMust be greater than 4 dB for reliable operationBoth 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 dataThese are automatically filtered outLarge numbers of spikes (> 10% of samples) is a problem

• Aerated water• Interference from submerged object

Smart QC

σV : Standard error of velocity

Measures variation in velocity during the averaging periodVaries with the environmentHigher in high velocity or highly turbulent environmentSmartQC automatically adjusts criteria to the environmentσV 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

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

Smart QC

Boundary QCAcoustic interference from underwater obstaclesIf possible, FlowTracker adapts operation to avoid interferenceIf a warning given, re-position probe and try again

Smart QC

Smart QC SummaryFor most warnings

Evaluate probe location, consider moving probeRepeat measurement

If problem persistsCheck probe operation (Auto QC, BeamCheck)Maybe there is not a problem

• Higher turbulence • High measurement angle• Aerated water• Locally high sediment load

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

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

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 (°)

Additional Firmware Features

• Data export• BeamCheck• Recorder download

International language support

Windows 2000/XP/Vista compatibility

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)

Discharge Report: Page 1-2

HTML-based reporting

Fully customizable

Easily translates to 7 different languages

Discharge Report: Page 1-3

Discharge Uncertainty

Background

Two Uncertainty Calculations

ISO Uncertainty Calculation

Statistical Uncertainty Calculation

Why 2 Calculations? Comparison of Results

Displaying Uncertainty Results

Discharge Uncertainty

What is uncertainty?How accurate is the discharge measurementMost agencies record a subjective measurement

qualityThis 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.

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)

Discharge Uncertainty

Statistical Uncertainty Calculation:

Developed by researchers at the U.S. Geological SurveyTim Cohn, Julie Kiang, and Robert MasonNew technique, limited publications and field

experienceAlso called “Interpolated Variance Estimated (IVE)

method

Fundamentally Different Approach:ISO: Physical properties of the measurement and

calculation

Statistical: Use adjacent measurements to estimate uncertainty

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

D i-1 D i D i+ 1

Δ i

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

Unce

rtain

ty

Statistical Uncertainty (%)

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

Discharge Uncertainty

Firmware (Real-Time)

Overall Uncertainty

Largest Source

TotalQ 5.2015 m3/s RatedQ 5.3500 m3/sDifference -2.8%0=Exit or Enter=More

Q Uncertainty 3.1% Largest Source Velocity0=Exit or Enter=More

Software (Post-Processing)

Overall Uncertainty

Contribution of Each Source

Questions?