Industrial · Material Inspection

Structure read from the outside.

The same capacitive physics that images multiphase flow inside vessels — adapted for solid media. Voids, cracks, delaminations, and composition gradients resolved within structures that cannot be opened, irradiated, or taken out of service.

From fluid dynamics to solid matter

The physics that images flow inside vessels also reads the interior of solid structures.

The transition from process imaging to material inspection is not a change in physics but in the state of the medium. Where process imaging targets dynamic multiphase flow, material inspection targets solid structures whose internal properties — voids, discontinuities, composition gradients, delaminations — are fixed in space but invisible from the exterior.

The measurement challenge in solid media is signal magnitude. Capacitance readings at dense solid boundaries are orders of magnitude smaller than in fluid systems. Genuine structural signals are buried in parasitic noise unless measurement architecture is redesigned at the circuit level. T-configuration CMOS switching was developed to address this directly, engineered specifically to strip stray capacitance out of the hardware: parasitic stray capacitance is eliminated in hardware — not corrected in software — exposing the genuine dielectric contrast within the material at sub-femtofarad precision.

A systematic comparison of ECVT sensor geometries identified planar and conforming configurations as optimal for flat structures and curved surfaces respectively. The 3D sensitivity matrix modification — originally developed to improve axial resolution in process imaging — also addresses the depth-resolution challenge in solid media inspection, where signal perturbation from an internal anomaly decreases with distance from the sensor surface. Applied to soil water infiltration, this same framework demonstrated its reach into permittivity distributions within media far denser than industrial fluid systems.

From surface to structure

Structural mapping from a single external face.

01 — Sensor sits on the surface Planar or conforming array 02 — Switching cancels stray signal T-config switch sub-fF resolution Parasitic capacitance stripped out 03 — Contrast localised by depth Void, crack, or delamination isolated 04 — Permittivity map resolves Voids, cracks, gradients — spatially resolved
01
Planar or conforming sensor
Array placed against the external surface — no drilling, no coating removal, no interior access. Geometry selected from Baidillah's sensor comparison: planar for flat structures, conforming for curved.
02
T-config parasitic cancellation
CMOS switching in T-configuration eliminates parasitic stray capacitance at circuit level before the signal reaches reconstruction — exposing genuine dielectric contrast at sub-femtofarad levels.
03
Differential capacitance measurement
Dielectric contrast between sound material and anomalies resolved: voids carry near-zero permittivity; cracks and delaminations interrupt material continuity. 3D sensitivity matrix localises depth.
04
Permittivity map
3D reconstruction of the inspected volume. Voids, cracks, delaminations, and composition gradients spatially resolved — without cutting, without extraction, without radiation.
What the sensor reveals

The signal inside dense solid media that conventional NDT cannot extract.

In dense solid materials, a void the size of a human hair creates a permittivity perturbation that, without hardware-level cancellation of parasitic sources, is indistinguishable from switching noise. T-configuration CMOS switching addresses this as a circuit architecture decision — not as a software filter applied after measurement. The result is sub-femtofarad precision in conditions where standard ECT systems would yield only noise.

The same framework that Baidillah, Mukhlisin, and Taruno applied to soil water infiltration — a medium with far greater density and lower dielectric contrast than industrial fluids — validates the measurement sensitivity in challenging solid permittivity environments. Sensor geometry selection from the 2013 comparison work ensures that the sensitivity distribution reaches the required inspection depth without resolution loss at the critical internal boundary.

Structures addressed

Where conventional NDT cannot reach.

Particularly suited to infrastructure where access is constrained and radiation is impractical.

Weld Integrity

Internal void and crack detection in welds — without cutting sections, without radiographic exposure, without removing the structure from service.

Composite Laminates

Internal delamination, void pockets, and fibre discontinuities in composite structures — resolved from the external surface using conforming sensor geometry.

Post-Tensioned Tendons

In-service assessment of post-tensioned tendons in concrete — no coring, no drilling, no shutdown. Sub-surface inspection from a single external face.

Pipeline Wall

Wall thickness variation, internal corrosion, and lining integrity in pressurised or externally coated pipelines — inspection without coating removal or process interruption.

Concrete & Masonry

Void detection and reinforcement mapping within concrete and masonry — planar sensor on external face, 3D permittivity reconstruction of the interior.

Subsea & Coated Structures

Inspection through protective coatings and linings — no surface preparation beyond basic cleaning. No radiation hazard in confined or subsea environments.

Related publications

2013

Comparison of Sensor Geometries for Electrical Capacitance Volume Tomography

Int'l Journal of Innovative Computing, Information and Control 9 (11), 1447-1457
Baidillah M.R., Mukhlisin M., Taruno W.P.
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2012

ECVT for Measurement of Soil Water Infiltration in Vessel Experiments

Hydrology and Earth System Sciences
Baidillah M.R., Mukhlisin M., Taruno W.P.
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2007

Electrical Capacitance Volume Tomography

IEEE Sensors Journal 7 (4), 525-535
Warsito W., Marashdeh Q., Fan L.S.
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2015

Design and Simulation of Quadrature Phase Detection in Electrical Capacitance Volume Tomography

TELKOMNIKA 13 (1), 55-64
Muttakin I., Yusuf A., Rohmadi, Widada W., Taruno W.P.
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2016

Switch Configuration Effect on Stray Capacitance in Electrical Capacitance Volume Tomography Hardware

Int'l Journal on Smart Sensing and Intelligent Systems
Yusuf A., Muttakin I., Widada W., Taruno W.P.
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2017

Design of Capacitive Sensor, Measurement and Data Acquisition System of ECVT

IOP Conference Series: Materials Science and Engineering
Yusuf A., Widada W., Taruno W.P.
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2016

Analysis of Excitation Frequency to Performance of Electrical Capacitance Tomography

Journal of Physics: Conference Series
Yusuf A., Muttakin I., Widada W., Taruno W.P.
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2015

Hardware Implementation of Linear Back-Projection Algorithm for Capacitance Tomography

ICICI-BME 2015, pp. 124-129
Herdian H., Muttakin I., Saputra A., Yusuf A., Widada W., Taruno W.P.
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2024

Characterization of Magnetic Induction Tomography Sensor for Weld Defect Inspection on Steel Plates

Jurnal Fisika dan Aplikasinya
Haryono D., Sholehah A., Suwandana R.F.
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