NDT Master is an offline ultrasonic testing calculator designed for weld inspectors, NDT technicians and engineering students. This page documents how the app calculates each value, which standards it references, and how to get support.
NDT Master is a calculation and visualization tool for ultrasonic testing (UT) used in weld inspection, raw material examination and component qualification. It runs entirely on-device. There is no account, no cloud sync, and no third-party analytics.
The app is intentionally narrow in scope. It is not an inspection record system, an instrument controller, or a substitute for qualified personnel. It is a fast, reviewable calculator that a Level I/II/III inspector can use on site to cross-check a near-field length, plot a refracted angle, or build a quick DAC/TCG reference.
Design priorities, in order: correctness of the underlying physics → fast input on a phone with one hand → readable output in bright outdoor light → no surprises with units or sign conventions.
All calculations are derived from published acoustic-physics formulas and standard NDT practice. The app references the following standards as the basis for terminology, geometric conventions and acceptance-criteria workflows:
Internally, every calculation is performed in SI base units (m, s, Hz, kg/m³). Conversions to mm / MHz / inch / ft happen only at the display layer through Foundation.MeasurementFormatter, which means region-specific unit preferences cannot introduce numerical drift into intermediate results.
Default longitudinal- and shear-wave velocities ship with values cited from the standards above and from widely-used NDT handbooks (e.g. Krautkrämer & Krautkrämer, Ultrasonic Testing of Materials; ASNT Nondestructive Testing Handbook, Vol. 7). Users can edit any material or add custom alloys; custom values are stored locally only.
Inspection environments — tank farms, pipeline right-of-ways, refinery shutdowns, offshore platforms — are routinely without reliable network. The app is engineered to give the same result on a disconnected device that it would on a connected one. There is no remote calculation server, by design.
The formulas below are the exact expressions used in production. Sign conventions and geometry follow common UT field practice (probe index at origin, beam centerline measured from the normal, second-leg distance accumulated through skip).
For DAC, the app fits a smooth curve through user-provided reference reflector points (side-drilled holes or flat-bottom holes at increasing depth), and renders the −6 dB and −14 dB evaluation lines per ASME BPVC V Article 4 Mandatory Appendix VII. For TCG, the gain compensation values along the sound path are derived from the same reference data so that an equal-amplitude reflector reads at the same screen height at any depth.
Numerical accuracy of the underlying expressions is limited only by 64-bit floating-point precision (about 15 significant decimal digits). The accuracy of the physical result in your inspection depends on inputs: material velocity, probe diameter, refracted angle and reference level all carry uncertainty in practice. The app reports calculated values to a precision that does not overstate input uncertainty (typically 2–3 decimals in mm, 0.1 dB).
The arithmetic (a − b − c with the path-length attenuation correction) has been stable across AWS D1.1 editions for many years. Acceptance class tables (8.2 / 8.3) are presented for reference; you remain responsible for confirming against the contract edition applicable to your project (e.g. AWS D1.1:2020 vs. earlier).
The DAC module uses the user-supplied reference reflector amplitudes at known depths to construct the primary curve, then offsets by −6 dB and −14 dB to render the evaluation and recording lines per ASME BPVC V Article 4 Appendix VII. The curve is generated by monotone piecewise interpolation between points; the underlying point data and the gain offsets are always shown so the curve can be cross-checked by hand.
Instrument screen layouts vary widely, but the three numeric fields most often manually re-typed during a job are velocity (m/s or in/µs), frequency (MHz) and gain (dB). OCR is scoped to these on purpose: a narrow, well-tested capture surface is more reliable than a general "read anything on the screen" feature. You can always reject the OCR suggestion and type the value.
No. All calculations and OCR run on-device. No inspection inputs, history, custom materials, OCR images or analytics events are sent to any server. The app does not contain third-party advertising or analytics SDKs in the current release. See the Privacy Policy for the full statement.
Calculation results, DAC reference data and history records can be exported as CSV or PDF (Pro tier). The export format is plain and intentionally human-readable so that the values can be pasted into a company report template or attached as supporting evidence.
Yes. The Materials section lets you create custom entries with longitudinal- and shear-wave velocities and density. Custom materials are stored only on your device. Up to 100 custom entries are supported.
Basic unlocks the full set of everyday UT calculators (wavelength, near field, beam spread, Snell's law, flaw location, dB, impedance, resonance, ToFD PCS) plus material presets and local history. Professional adds AWS D-Rating, DAC/TCG curve construction, the OCR scanner, advanced 3D beam-path visualization, and report-ready CSV/PDF export. Both are one-time purchases — there is no subscription.
Yes. The app is universal and supports iPad split-view. On a 12.9" iPad Pro a two-pane layout is used where applicable so the calculator and the 3D beam view can be visible at the same time.
The 3D beam simulation uses SceneKit. On A10–A11 class devices the simulation is rendered at a reduced framebuffer scale so that 60 fps is preserved during slider interaction. The numerical results are identical regardless of device class.
Email st67891@gmail.com with: the calculator name, every input value with its unit, the value the app produced, and the value you expected (with your derivation or reference). We take calculation issues seriously and aim to confirm or fix within one business day.
Yes — for NDT training providers, technical colleges and ASNT/ISO 9712 prep courses we can arrange volume licensing and instructor briefing materials. Please contact us with your institution name, expected number of seats and the course it will be used in.
This should not happen — history is stored in the app's local container and is preserved across iOS updates. If you observe it, please contact us with the iOS version (before and after) and the approximate count of records lost. We will investigate immediately.
When reporting an issue, please include: iOS version, device model (e.g. iPhone 14 Pro), app version (Settings → About), the calculator/feature involved, every input value with its unit, the observed result, and the expected result with your reference if you have one.
NDT Master is a calculation aid, not a qualified inspector. Outputs are produced by deterministic formulas and the precision of your inputs. They do not replace the judgement of qualified personnel (ASNT SNT-TC-1A / NAS 410 / ISO 9712 Level II or III as appropriate), a written procedure, or the acceptance criteria of the applicable code edition.
© 2026 NDT Master. All rights reserved. The NDT Master app and related materials — including software code, UI design, text content, graphics and documentation — are protected by applicable copyright and intellectual property laws.
Use of NDT Master is governed by the applicable Apple Media Services Terms and any end-user license terms provided in the App Store listing and in-app legal sections. Unless explicitly permitted by law or written authorization, you may not:
"NDT Master" and associated branding elements are the property of their respective owner(s). Apple, App Store, iOS, iPhone and iPad are trademarks of Apple Inc. AWS, ASME, EN, ISO and GB/T are referenced for informational interoperability only and remain the property of their respective standards-development organizations. All other trademarks belong to their respective owners.
The app references industry standards (AWS, ASME, EN, ISO, GB/T) for terminology, geometric conventions and workflow assistance. NDT Master does not reproduce protected standard text. Users remain responsible for obtaining and complying with the applicable standard in their jurisdiction and inspection scenario.
To the extent permitted by law, the app is provided "as is" without warranties of uninterrupted operation, fitness for a particular purpose, or suitability for any specific industrial case. Engineering decisions based on the app's output must be reviewed by qualified personnel.