OTT ADC Acoustic Digital Current Meter:

Description of meter and Results of USGS testing

Dan Wagner

Hydrologist

Arkansas Water Science Center

Hydroacoustics WebinarMay 24, 2010

Outline

• Description of ADC• Results of USGS Testing• New USGS Firmware / enhancements

ADC History

• Released in USA December 2007 • Testing by HIF, HAWG, and WSCs from

2008-2010• New 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

ADCADV

Measuring Principle

Two 6 MHz acoustic transducers

Large sample volume located in front of sensor– Large sample volume reduces

potential signal-to- noise (SNR) issues, reduces error with flow angles

Two sample volumes– Improves data precision– Internal 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 CorrelationCheck for similaritiesCalculation of time shift

Dt

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 automatically

• Hand-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 checks

• With 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 MeasurementsSite Vmean,ADV Vmean,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 Vmean,ADV Vmean,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

0 0.5 1 1.5 2 2.5

-60

-50

-40

-30

-20

-10

0

10

20

Vmean, ADC in ft/s

Percent dif-ference from Vmean, ADV

0.00 0.50 1.00 1.50 2.00 2.50-50.00

-40.00

-30.00

-20.00

-10.00

0.00

10.00

20.00

30.00

40.00

50.00

Percent Difference of Velocity Measured with ADC Relative to Velocity Measured with ADV

Mean Stream Velocity, in feet per second

Dif

fere

nce

, in

per

cen

t

Figure courtesy of Kevin Oberg, OSW

0.00 100.00 200.00 300.00 400.00 500.00 600.00 700.00 800.00-50.00

-40.00

-30.00

-20.00

-10.00

0.00

10.00

20.00

30.00

40.00

50.00

OTT ADC Percent Difference vs. Discharge

Discharge, in cubic feet per second

Dif

fere

nc

e,

in %

Figure courtesy of Kevin Oberg, OSW

0.00 0.50 1.00 1.50 2.00 2.500.00

0.50

1.00

1.50

2.00

2.50

Velocity vs. Velocity Plot

FlowTracker Velocity, in feet per second

OT

T A

DC

Ve

loc

ity

, in

fe

et

pe

r s

ec

on

d

Figure courtesy of Kevin Oberg, OSW

0.00 0.50 1.00 1.50 2.00 2.500.00

0.50

1.00

1.50

2.00

2.50

Depth vs. Depth Plot

FlowTracker Depth, in feet

OT

T A

DC

De

pth

, in

fe

et

Figure courtesy of Kevin Oberg, OSW

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0-12%

-10%

-8%

-6%

-4%

-2%

0%

2%

4%

6%

8%

10%

12%

ADC Tow Tank Testing (tow speeds 0.10 ft/s to 8 ft/s)2010-03-10; 1020 and 250176

2010-03-11; 1028 and 1029

Accuracy Limits 1020 Data 1020 Mean 250176 Data 250176 Mean

1028 Data 1028 Mean 1029 Data 1029 Mean

Tow Speed (ft/s)

Per

cet

Err

or

1020 - 6 m cable1028 - 10 m cable1029 - 2.5 m cable250176 - 2.5 m cable

Figure Courtesy of Kirk Thibideaux, HIF

-90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90-25.0%

-20.0%

-15.0%

-10.0%

-5.0%

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

Cosine Errors (Vertical Angles) at 2 fps

ADC 1029 (2010-02-16) ADC 250176 (2010-02-17) ADC 1020 (2010-02-18) ADC 1028 (2010-02-19)

Angle Turned (Deg.)

Pe

rce

nt

Err

or

Figure Courtesy of Kirk Thibideaux, HIF

-60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60-10.0%

-8.0%

-6.0%

-4.0%

-2.0%

0.0%

2.0%

4.0%

6.0%

8.0%

10.0%

Cosine Errors (Horizontal Angles) at 3.2 fps

1020 (2010-03-01) 1028 (2010-03-05) 1029 (2010-03-08) 250176 (2010-03-08)

Angle Turned (Deg.)

Pe

rce

nt

Err

or

Figure courtesy of Kirk Thibideaux, HIF

ADC Pros/Cons-prior to USGS firmware

Pros:• Depth Sensor• Sample volume in front of meter• Rugged Construction, cabling• Rechargeable battery• 2 beams-improved performance

in environments with low SNR, angles

• Live velocity reading-can help with meter placement

Cons:• Depth Sensor• Sample volume in front of meter• Rechargeable battery (?)• Can’t edit erroneous stations until

reviewing the measurement in Qreview

• Lack 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 assurance

– Including pre-deployment quality check and field quality check• Ability to enter rated Q• Expanded character limits for station name and number

and addition of measurement number• Computation and recording of averaged flow angles• On-screen warning messages, a.k.a., Measurement

Guidance– Provide user with options to improve measurement results

• Option to turn off depth sensor• Enhanced measurement review

– Detailed discharge and quality check reports– Warning and potential quality issue logs– One-second time series data

New ADC QA/QC Warnings

Figure courtesy of OTT

Questions?