1. EPOCH 1000 Series Procedure Phased Array DGS/AVG

2. PA DGS/AVG Feature Overview
The EPOCH 1000i offers the DGS/AVG sizing feature standard for phased array mode:
Standard EPOCH onboard DGS/AVG setup menu
Applies DGS/AVG curve at 0°, 45°, 60°and 70°focal laws
Quick setup using modified GAIN calibration tool
Interpolated image TVG for easy detection across soundpath range
Use PA probe ID and wedge information to establish curve characteristics

3. Required Items Transducer and Wedge 5L16-9.6X10-A10P-P-2.5-OM probe
SA10P-N55S wedge
Test Block
EP1000-PABLOCK-1
Couplant
D-12

4. Feature Activation
Proper calibration is required prior to activation of the DGS/AVG feature for precise measurements

5. Feature Activation
The DGS/AVG activation is located in the SIZING OPTION menu group under [P2] (DGS)
The DGS/AVG menu is used to establish the following DGS setup parameters:
Reflector Type
Reflector Diameter
Delta Vt
Registration Level
Warning Level
ACVSpecimen
ACVCalBlock
Delta Vk (radius only)
Note that due to PA probe automatic recognition and wedge selection during Beam setup, probe information does not need to be configured in the DGS/AVG screen

6. *used only with Angle Beam probe **used only with Straight Beam probe
DGS/AVG Parameters
DGS/AVG setup includes up to 8 parameter selections/adjustments before the operator can begin inspections:
Reflector Type – A single reference reflection is required to build the DGS curve(s) on the EPOCH 1000i – this can be from a Backwall**, Flat-Bottom Hole (FBH), Side-Drilled Hole (SDH), K1/IIW Block Radius*, or K2/DSC Block Radius*
Reflector Diameter – When a Reflector Type of SDH or FBH is selected, the operator must indicate the size of the reference hole.
Delta VT – Also known as Transfer Correction, Delta VT is a calculated value the accounts for an overall attenuation difference between a reference/calibration block and the actual inspection piece (typically caused by surface conditions or subtle material variation)
Registration Level – The value of the “critical” reference reflector for the inspection. This defines the relative height of the DGS curve and the comparison to unknown flaw reflections for rejection/acceptance criteria.
*used only with Angle Beam probe **used only with Straight Beam probe 6

7. DGS/AVG Parameters
Warning Level – DGS/AVG allows for one Warning Curve in addition to the main DGS curve. This can be set from +6.0dB to -14.0dB below the main curve, or to 0.0dB to turn this curve off.
ACV Specimen – An attenuation compensation value for the inspection piece. This value is used to adjust the DGS curve, which is based on attenuation in an “ideal” or “perfect” carbon steel, to reflect accurate attenuation response in a “real-world” test piece. This is especially important for longer sound paths. The calculation for this attenuation adjustment is defined in the code EN 583 and other documents.
ACV Calibration Block – An attenuation compensation value for the calibration block. This value serves the same purpose as ACV Specimen, but is used when capturing a reference reflector from the calibration block.
NOTE: ACV Specimen and Calibration Block values are single values applied to all curves 7

8. Feature Activation
When using the Aluminum PA Demo Block for demonstration, use the DGS/AVG menu to establish the following DGS setup parameters:
Reflector Type = SDH
Reflector Diameter = 1.5mm
Delta Vt = 0.0dB
Registration Level = 1.00mm
Warning Level = 0.0dB
ACVSpecimen = 0.0dB/m
ACVCalBlock = 0.0 dB/m
Delta Vk (radius only) = NA
After hitting ESC, the unit will provide the following prompt. Select NO for full procedure.

9. Acquiring DGS Setup Point
As with the conventional DGS/AVG feature, one of the main advantages of this technique is the requirement of only one reference reflector to perform full curve setup
Place the 5L16 probe on top of the demo block, over the second most shallow SDH, and facing the closest side of the block

10. Acquiring DGS Setup Point (cont.)
After exiting the DGS/AVG activation menu, the instrument will default to the PA CAL group, with the Calibration type DGS active
Use the same procedure as GAIN calibration to acquire the first SDH as the DGS reference reflector:
Set reference cursor to 45 degrees
Position Gate 1 to capture an amplitude measurement from the SDH across all angles
Use AUTO 80% to bring the SDH reflection to 80% at 45 degrees
Press [P1] (ADD) to begin point calibration
Press [P2] (DONE) after successful acquisition of point

11. DGS/AVG Reference Point Collection

12. DGS/AVG Menu
Once the DGS reference reflector has been acquired, the DGS group menu appears beside [F3] (DGS) in group 4/5
P1 – Live adjustment of registration level
P2 – Live adjustment of transfer correction (Delta Vt)
P3 – Toggles scanning gain on and off
P4 – Toggles sector scan interpolated TVG on and off
P7 – Turns DGS function OFF without entering a setup menu

13. Sector Scan Image Correction
A unique feature of Phased Array DGS/AVG on the EPOCH 1000i is the ability to interpolate image gain correction across all angles and soundpaths based on the reference reflector
This gain correction allows the DGS/AVG user to gain the benefits of higher probability of detection through the sector scan image while still maintaining mathematically correct DGS/AVG curves at standard A-scan angles for sizing.

14. Phased Array DGS/AVG and the EPOCH 1000i
When adjusting focal laws/angles in DGS/AVG mode
Coarse adjustment switches only to focal laws with curves applied to the A-scan (0°, 45°, 60°and 70°)
Fine adjustment allows access to all focal laws, but curves are only displayed for A-scans at 0°, 45°, 60°and 70°
PA DGS/AVG curves may also be used with fixed angle linear scans at 0°, 45°, 60°and 70°

15. Important Phased Array DGS/AVG Notes
ERS Measurement: Remember that the digital ERS (equivalent reflector size) measurement in DGS/AVG is not the same as dB to Curve in DAC mode!
Each curve represents attenuation of sound using a Flat Bottom Hole target
The digital ERS measurement of a live signal rates the signal as if it were a FBH. This means that if the operator sets the curve registration level to 1.5mm and sizes a 1.5mm side drilled hole, the echo will not meet the level of the DGS curve, and the ERS measurement will not be 1.5mm!
Material: The DGS/AVG curves are based on clean steel. Especially when using the Aluminum PA Demo Block, the echo will not align with the DGS curve properly. The PA Demo Block is for general demonstration of this feature only!