Phased Array UT (PAUT) Level II Practice Questions

30 original questions in 6 topics, each with the correct answer, an explanation and its basis. Last reviewed October 16, 2026.

About this PAUT Level II practice test

These 30 multiple-choice questions are original study questions written by Atlantis NDT for phased array technicians working toward Level II. They are not ASNT exam questions. They follow the Level II job: build and verify the set-up, calibrate wedge delay, ACG and TCG, run encoded scans to a scan plan, analyze the data, size indications and report against a procedure.

Under ASNT SNT-TC-1A (2024 edition), the employer certifies Level II technicians after general, specific and practical examinations defined in its written practice, which sets the PAUT training and experience it requires. ASNT's central ASNT NDT Level II examinations include UT but do not list PAUT as a separate technique, so the PAUT examinations come from the employer's written practice. A good grounding in conventional UT is assumed.

Atlantis NDT runs NDT training year-round, with theory online and hands-on practice on its Practical NDT simulator or in person at the client's own facility. Simulator practice supports training; it does not replace the practical examination or the experience hours the employer's written practice requires.

How to use this practice test

  • Answer each question before opening the explanation.
  • Sketch the beam geometry for the calculation questions; a quick drawing catches most sine and cosine mix-ups.
  • Mark the topics where you miss questions and review them against your employer's procedure and scan plans.
  • Re-test after study and check that your weak topics have improved.

Topics in this set:

Practice questions, not exam questions

Atlantis NDT wrote these questions as original study material. They are not taken from ASNT or from any employer's examination, and real examinations differ in wording, emphasis and format.

Certification is a separate step: under ASNT SNT-TC-1A the employer certifies its technicians after the examinations its written practice sets, and ASNT runs central Level II examinations for several methods. A good score here is a study signal, not a qualification.

Phased array principles

Question 1. How does a phased array instrument steer the ultrasonic beam to a chosen angle?

  1. A. By mechanically rotating the element array inside the probe housing to the chosen angle
  2. B. By delaying each element's pulse and signal so the wavefronts combine at that angle
  3. C. By driving each element at a slightly different frequency across the array
  4. D. By changing the couplant thickness under the wedge
Show answer

Correct answer: B. By delaying each element's pulse and signal so the wavefronts combine at that angle

Steering and focusing come from constructive interference: the instrument delays each element's pulse, and its received signal, according to a focal law. Frequency and couplant are not the steering mechanism.

Basis: General PAUT principle

Question 2. In phased array testing, what is a focal law?

  1. A. The code clause that sets the acceptance criteria for phased array indications
  2. B. The maximum steering angle printed on the probe label for that wedge and frequency
  3. C. The rule that the near field of each element equals D²·f/(4v)
  4. D. The active elements and delays used to form one beam at a given angle and focus
Show answer

Correct answer: D. The active elements and delays used to form one beam at a given angle and focus

Each beam in a sectorial or linear scan is produced by its own focal law. The instrument calculates the laws from the probe, wedge and material data entered by the operator, which is why those inputs must be correct.

Basis: General PAUT principle

Question 3. Which condition helps keep grating lobes low in a phased array probe?

  1. A. A pitch small relative to the wavelength, with steering kept within the design range
  2. B. An element pitch several times larger than the ultrasonic wavelength in the test material
  3. C. Raising the frequency while keeping the same element pitch and aperture
  4. D. Using the largest steering angles the instrument and wedge allow
Show answer

Correct answer: A. A pitch small relative to the wavelength, with steering kept within the design range

Grating lobes appear when the pitch is large relative to the wavelength and grow at large steering angles. Raising the frequency shortens the wavelength, which makes the same pitch relatively larger and worsens grating lobes.

Basis: General PAUT principle (grating lobes)

Question 4. At a fixed frequency, what is the general effect of increasing the active aperture (using more elements per focal law)?

  1. A. The near field becomes shorter and the beam spreads more beyond it
  2. B. Deeper focusing becomes possible, with a narrower beam at the focus
  3. C. Sensitivity always decreases because the pulse is spread over more elements
  4. D. The beam can no longer be steered
Show answer

Correct answer: B. Deeper focusing becomes possible, with a narrower beam at the focus

A larger aperture lengthens the near field, and focusing is only effective within the near field, so a larger aperture allows deeper focusing and a smaller focal spot. It also usually increases sensitivity.

Basis: General PAUT principle (aperture and focusing)

Question 5. What distinguishes a linear (electronic) scan from a sectorial scan?

  1. A. A linear scan sweeps one aperture through a range of angles; a sectorial scan steps it along the array
  2. B. A linear scan can only be used at 0°, while a sectorial scan needs a wedge
  3. C. A linear scan steps the aperture along the array at one angle; a sectorial scan sweeps the angle
  4. D. There is no difference; the terms are interchangeable
Show answer

Correct answer: C. A linear scan steps the aperture along the array at one angle; a sectorial scan sweeps the angle

In a linear scan the same focal law is stepped across the array, so the beam moves sideways at a constant angle, which can be 0° or an angled beam on a wedge. In a sectorial scan the aperture stays fixed and the angle changes.

Basis: General PAUT principle (scan types)

Set-up and calibration

Question 6. What does wedge delay calibration correct for in a sectorial scan?

  1. A. The time each focal law spends in the wedge, so zero depth is the part surface
  2. B. Attenuation in the test material, which grows at the higher refracted angles
  3. C. Differences in frequency and sensitivity between the elements of the array
  4. D. Electrical noise picked up in the probe cable and connector
Show answer

Correct answer: A. The time each focal law spends in the wedge, so zero depth is the part surface

Each angle travels a different path through the wedge. Wedge delay calibration, usually on a known radius or side-drilled hole, sets the time zero for every focal law so that depths and sound paths are correct across the sector.

Basis: General PAUT calibration practice

Question 7. What is the purpose of angle-corrected gain (ACG) in a sectorial scan?

  1. A. To make the back-wall echo the same screen height at every depth
  2. B. To remove grating lobes from the higher steering angles
  3. C. To correct the depth readout for curved or uneven scanning surfaces
  4. D. To give the same reflector the same amplitude on every angle
Show answer

Correct answer: D. To give the same reflector the same amplitude on every angle

Without ACG the response from a given reflector varies with angle because of wedge path, transmission and beam effects. ACG, commonly set on a radius or side-drilled hole, equalizes the angles so amplitudes can be compared across the sector.

Basis: General PAUT calibration practice

Question 8. How does time-corrected gain (TCG) differ from a DAC curve?

  1. A. TCG is used only for straight beams, while a DAC is used only for angle beams
  2. B. TCG adjusts gain with time so equal reflectors show equal height; a DAC keeps gain fixed and draws a curve
  3. C. TCG is drawn on the screen as a falling curve, whereas a DAC is a horizontal line
  4. D. TCG removes the need for a calibration block, whereas a DAC requires one
Show answer

Correct answer: B. TCG adjusts gain with time so equal reflectors show equal height; a DAC keeps gain fixed and draws a curve

Both are built from the same type of reference reflectors at different depths. With TCG the reference level becomes a constant screen height across the depth range, which suits color-coded S-scan and C-scan displays.

Basis: General PAUT calibration practice

Question 9. Why is encoded scanning important in PAUT weld examination?

  1. A. It increases the effective probe frequency during scanning
  2. B. It removes the need for couplant on smooth surfaces
  3. C. It ties every A-scan to its position on the weld for length sizing and later review
  4. D. It lets the software accept or reject indications automatically against the code limits
Show answer

Correct answer: C. It ties every A-scan to its position on the weld for length sizing and later review

Encoding gives every data point a position, which is what makes C-scans, length sizing and independent re-analysis of the stored data possible. Evaluation is still done by the qualified analyst.

Basis: General PAUT practice; ASTM E2700

Question 10. An encoder is checked by moving the scanner along a measured 500 mm. The instrument displays 495 mm. What is the encoder error?

  1. A. 0.5%
  2. B. 1.0%
  3. C. 5.0%
  4. D. 10%
Show answer

Correct answer: B. 1.0%

Error = (500 − 495) ÷ 500 × 100 = 1.0%. The procedure states the allowed tolerance; if it is exceeded, the encoder is recalibrated before scanning.

Basis: General PAUT practice (encoder calibration)

Question 11. A sectorial scan is set from 40° to 70° in 0.5° steps. How many focal laws does it contain?

  1. A. 30
  2. B. 31
  3. C. 60
  4. D. 61
Show answer

Correct answer: D. 61

(70 − 40) ÷ 0.5 = 60 steps, and counting both end angles gives 60 + 1 = 61 focal laws. Forgetting the starting angle gives the common wrong answer of 60.

Basis: General PAUT set-up

Scan planning and coverage

Question 12. On a 25 mm plate, the 55° beam of a sectorial scan shows a reflector at a sound path of 40 mm. Where is the reflector relative to the probe index point?

  1. A. Depth about 22.9 mm, surface distance about 32.8 mm
  2. B. Depth about 32.8 mm, surface distance about 22.9 mm
  3. C. Depth about 27.1 mm, surface distance about 32.8 mm
  4. D. Depth 40.0 mm, directly below the index point
Show answer

Correct answer: A. Depth about 22.9 mm, surface distance about 32.8 mm

Depth = 40 × cos 55° ≈ 22.9 mm, which is less than the 25 mm thickness, so the reflector is on the first leg. Surface distance = 40 × sin 55° ≈ 32.8 mm. Option B swaps sine and cosine; option C would only apply on the second leg.

Basis: Angle-beam geometry

Question 13. Why must the probe offset (distance from the probe index or wedge front to the weld centerline) be set correctly and recorded?

  1. A. It sets the probe frequency used by the focal laws
  2. B. It is only needed for thickness measurement and has no effect on weld coverage
  3. C. It determines the wedge velocity used in the focal-law calculation
  4. D. Weld coverage depends on it, and the software uses it to place indications
Show answer

Correct answer: D. Weld coverage depends on it, and the software uses it to place indications

The scan plan's coverage is only achieved at the planned offset, and the analysis overlay places indications using it. A wrong offset can leave part of the weld unexamined and mislocate indications.

Basis: General PAUT practice (scan plan)

Question 14. What is the main purpose of a PAUT scan plan with a beam-coverage (ray-trace) drawing?

  1. A. To show the probes, angles, focal depths and offsets cover the weld and heat-affected zone
  2. B. To record the technician's training hours and the equipment serial numbers
  3. C. To list the acceptance criteria that apply to each type of indication
  4. D. To replace calibration on a reference block once the plan is approved
Show answer

Correct answer: A. To show the probes, angles, focal depths and offsets cover the weld and heat-affected zone

The scan plan demonstrates, before scanning, that the set-up will examine the required volume. It does not replace calibration, and the acceptance criteria come from the code or specification.

Basis: General PAUT practice; ASTM E2700

Question 15. Why are PAUT weld scans often performed from both sides of the weld?

  1. A. To double the amount of data stored for archiving and audit
  2. B. Because from one side, planar flaws on the far fusion face may be missed
  3. C. Because the encoder only counts distance in one direction along the weld
  4. D. Because grating lobes appear only on the side the probe faces
Show answer

Correct answer: B. Because from one side, planar flaws on the far fusion face may be missed

Planar flaws such as sidewall lack of fusion are best detected with the beam near perpendicular to their face. Scanning from both sides gives favorable incidence on both fusion faces.

Basis: General PAUT practice (coverage)

Question 16. A one-line (single-pass) encoded PAUT scan is run parallel to the weld at a fixed probe offset. What provides coverage across the weld cross-section?

  1. A. Moving the probe toward and away from the weld during the scan
  2. B. Raising the gain at the end of the scan
  3. C. The range of angles (or apertures) swept electronically by the focal laws
  4. D. The encoder resolution
Show answer

Correct answer: C. The range of angles (or apertures) swept electronically by the focal laws

In a one-line scan the probe moves only along the weld; the electronic sweep of the sectorial or linear scan covers the cross-section. This is why the scan plan must confirm that the angle range and offset reach the whole volume.

Basis: General PAUT practice (one-line scanning)

Data analysis and sizing

Question 17. What should be checked first when reviewing a recorded PAUT data file, before evaluating indications?

  1. A. Data quality: coupling, missing lines, encoder distance and saturation
  2. B. Whether the file name and folder follow the client's naming convention
  3. C. The color palette and display layout chosen for the analysis views
  4. D. The number of indications already marked by another analyst
Show answer

Correct answer: A. Data quality: coupling, missing lines, encoder distance and saturation

Indications cannot be evaluated reliably in data with coupling loss, dropped lines or encoder slip. Sections with poor data quality are rescanned before analysis.

Basis: General PAUT practice (data quality)

Question 18. Which PAUT display shows the weld cross-section (depth against distance from the probe) at one position along the scan?

  1. A. The C-scan (top view)
  2. B. The A-scan alone
  3. C. The encoder position plot
  4. D. The S-scan (sectorial view)
Show answer

Correct answer: D. The S-scan (sectorial view)

The S-scan shows all angles at one scan position, corrected for angle so the weld cross-section can be overlaid. The C-scan is a plan view of amplitude or depth over the scanned area.

Basis: General PAUT practice (data views)

Question 19. With encoded PAUT data, how is the length of a weld indication usually measured?

  1. A. From the number of focal laws in the sector that show the indication
  2. B. Along the scan axis, between end points defined by the procedure
  3. C. From the peak height of the echo in the A-scan at the reference level
  4. D. From the width of the colored indication in the S-scan
Show answer

Correct answer: B. Along the scan axis, between end points defined by the procedure

Length lies along the scan direction, so it is measured on the encoded axis. The procedure defines how the ends are found, for example a 6 dB drop from the peak.

Basis: General PAUT sizing practice

Question 20. For a planar flaw whose upper and lower tips can be resolved, which method generally gives the most reliable through-wall height with PAUT?

  1. A. Comparing the flaw's peak amplitude with the TCG reference level on the best angle
  2. B. Measuring the indication length in the C-scan
  3. C. Taking the depth difference between the upper- and lower-tip diffraction signals
  4. D. Counting the color bands across the indication in the S-scan
Show answer

Correct answer: C. Taking the depth difference between the upper- and lower-tip diffraction signals

Tip signals give the positions of the flaw extremities directly. Amplitude depends on orientation and roughness as well as size, and length says nothing about height.

Basis: General PAUT sizing practice

Question 21. Why must the weld overlay in the analysis software use the correct thickness, bevel geometry and probe offset?

  1. A. So indications plot in their true place, separating geometric echoes from flaws
  2. B. So that the instrument can raise the frequency
  3. C. So that the data file can be compressed for archiving
  4. D. Because the overlay sets the acceptance criteria for each indication automatically
Show answer

Correct answer: A. So indications plot in their true place, separating geometric echoes from flaws

An accurate overlay lets the analyst see whether an indication lies on the root, cap, bevel or in the parent metal. A wrong overlay can make a root geometry echo look like a flaw, or the reverse.

Basis: General PAUT practice (analysis)

Question 22. A flaw signal in the recorded data is saturated (it exceeded the instrument's maximum displayable amplitude). What is the problem?

  1. A. The flaw length cannot be measured at all from the saturated data
  2. B. Its true peak is unknown, so amplitude evaluation is unreliable
  3. C. The encoder position for that scan line is lost
  4. D. The calculated flaw depth doubles on the affected focal laws
Show answer

Correct answer: B. Its true peak is unknown, so amplitude evaluation is unreliable

Once the signal is clipped, its real amplitude above the reference level cannot be read. The area is rescanned at lower gain, or recorded with enough amplitude range, as the procedure requires.

Basis: General PAUT practice (data quality)

Question 23. How does a lack of sidewall fusion typically appear in a sectorial scan?

  1. A. As many small spots scattered through the weld center, on all the angles
  2. B. Only on the 0° focal law, below the weld cap
  3. C. With the same response on every angle in the sector
  4. D. Along the bevel line, peaking on angles near normal to the fusion face
Show answer

Correct answer: D. Along the bevel line, peaking on angles near normal to the fusion face

Sidewall lack of fusion is planar and follows the bevel, so it plots on the fusion line and peaks on the angles that strike it squarely. Scattered small spots are more typical of porosity.

Basis: General PAUT interpretation

Codes, procedures and documentation

Question 24. Which ASTM standard is a practice for contact ultrasonic testing of welds using phased arrays?

  1. A. ASTM E2700
  2. B. ASTM E2373
  3. C. ASTM E309
  4. D. ASTM E1444
Show answer

Correct answer: A. ASTM E2700

ASTM E2700 covers contact PAUT of welds. ASTM E2373 covers TOFD, ASTM E309 covers eddy current examination of steel tubular products, and ASTM E1444 covers magnetic particle testing.

Basis: ASTM E2700

Question 25. Which change would normally require the PAUT procedure or scan plan to be revised, and requalified where the code requires it?

  1. A. A different technician on the same shift who holds the same certification and level
  2. B. A new batch of the same couplant from the same supplier
  3. C. Using a probe with a different element count, pitch or frequency, or another wedge
  4. D. Using a different method of post-examination cleaning
Show answer

Correct answer: C. Using a probe with a different element count, pitch or frequency, or another wedge

Probe, wedge and focal-law parameters change the beams produced and therefore the coverage and sensitivity, so codes treat them as essential variables. ASME Section V Article 4 lists such variables for UT procedures.

Basis: ASME BPVC Section V, Article 4 (procedure requirements)

Question 26. A PAUT Level II finds that the wedge specified in the approved scan plan is not available on site. What is the appropriate action?

  1. A. Use any available wedge with a similar nominal angle and simply note the change in the report
  2. B. Change the wedge velocity in the software until the S-scan image looks right
  3. C. Refer to the Level III; substitute only if the procedure or an approved revised plan allows
  4. D. Proceed without a wedge, scanning directly on the array face
Show answer

Correct answer: C. Refer to the Level III; substitute only if the procedure or an approved revised plan allows

A different wedge changes the focal laws and coverage. A Level II works within the approved procedure; changing an essential variable needs the procedure owner's revision and approval.

Basis: ASNT SNT-TC-1A (Level II and Level III responsibilities)

Method limitations

Question 27. Which statement describes a genuine limitation of PAUT compared with manual single-element UT?

  1. A. PAUT cannot detect planar flaws such as lack of sidewall fusion
  2. B. PAUT data cannot be recorded or reviewed after the scan
  3. C. PAUT cannot be used on butt welds in carbon steel
  4. D. An error in the probe, wedge or material data affects every calculated beam
Show answer

Correct answer: D. An error in the probe, wedge or material data affects every calculated beam

Every beam is calculated from operator inputs, so an error in probe, wedge, velocity or offset data affects all the results, which is why set-up and calibration demand more training and verification. PAUT detects planar flaws such as sidewall lack of fusion, records data for later review and is widely used on carbon steel butt welds.

Basis: General PAUT principle

Question 28. Why is the usable angular range of a sectorial scan limited, especially far from the wedge's nominal refracted angle?

  1. A. Because the encoder cannot record data from angles away from the nominal angle
  2. B. Because the probe frequency changes as the steering angle increases
  3. C. Because amplitude falls and grating or side lobes grow as the beam is steered further
  4. D. Because the couplant layer becomes thicker at the higher steering angles
Show answer

Correct answer: C. Because amplitude falls and grating or side lobes grow as the beam is steered further

Steering efficiency drops with steering angle, and ACG can raise amplitude but not remove lobes or restore beam shape. The scan plan should use angles within the range the probe and wedge handle well.

Basis: General PAUT principle (beam steering limits)

Question 29. For coarse-grained austenitic or dissimilar-metal welds, which PAUT configuration is commonly chosen to reduce scatter and noise?

  1. A. High-frequency shear-wave linear arrays with fine element pitch
  2. B. Dual (transmit-receive) arrays using low-frequency refracted longitudinal waves
  3. C. A single large shear-wave array at the highest frequency the instrument supports
  4. D. Surface-wave arrays placed on each side of the weld cap
Show answer

Correct answer: B. Dual (transmit-receive) arrays using low-frequency refracted longitudinal waves

Longitudinal waves at lower frequency are less affected by coarse, anisotropic grain structures, and separate transmit and receive arrays reduce wedge noise. High-frequency shear waves scatter more in these materials.

Basis: General PAUT practice (austenitic welds)

Question 30. When a small-diameter pipe circumferential weld is examined with a flat-bottomed wedge, what is the main risk?

  1. A. An increase in the effective probe frequency caused by the curved surface
  2. B. Loss of encoder counts, with no effect on the beam itself
  3. C. Poor coupling and beam distortion, so a contoured wedge is normally used
  4. D. An automatic change from a sectorial scan to a linear scan
Show answer

Correct answer: C. Poor coupling and beam distortion, so a contoured wedge is normally used

A flat wedge rocks on a curved surface, giving a thick, uneven couplant layer and an altered beam entry. Wedges contoured to the curvature keep coupling and beam geometry consistent.

Basis: General PAUT practice (curved surfaces)

Next step: PAUT Level 2 course

Practice questions check recall. Structured training adds the classroom and hands-on hours your certification route requires. The PAUT Level 2 course covers probe and wedge selection, focal-law set-up, sectorial and encoded scanning, and scan-plan execution. Completing a course is not certification: under an employer-based scheme such as SNT-TC-1A, your employer certifies you after its own examinations.

For employers: ASNT Level III consulting covers procedures, the written practice, qualification examinations and audit support for your technicians.

Where to go next

Atlantis NDT courses run year-round, with theory online and hands-on practice on the Practical NDT simulator or in person at the client's own facility. From here:

Enquire about PAUT Level II training for yourself or for a team. Tell us the method, the level and where the trainees are based.

Practise before the exam

Written papers test what you know; employers and practical examinations test what you can do with a probe in your hand. Use the free practice tests to find your gaps, then practise the technique.

Free downloads

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  • ExcelPhased array (PAUT) reportExcel workbook, written as Atlantis Engineering Consultants with no logo, so you can add your own.Download .xlsxAbout this template
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  • PDFUT Level II General practice questions40 questions. PDF with an answer key and explanations.Download PDF
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