Video Extensometer – Quantum Series

The Qualitest Quantum Series (Quantum-1-X* and Quantum-2-X*) operates on an optical tracking principle: as long as the specimen surface remains visible within the camera field of view, deformation is measured continuously without physical contact. This approach eliminates knife-edge slippage, avoids specimen misalignment, prevents surface scoring on thin foils or films, and protects the optical sensor during destructive specimen fracture.

[ Test Specimen Surface with Contrast Marks ]
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  [ Dual Shortwave Illumination Array ]
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  [ Telecentric / Optical Lens Assembly ]
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  [ High-Speed CMOS Sensor (22 to 1000 Hz) ]
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  [ Real-Time DIC and Pattern-Tracking Core ]
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  [ Real-Time Strain Output ]    [ Image Sequence Cache ]
  • Analog (±10V) & Digital I/O   • Post-Test Re-Analysis
  • Closed-Loop Strain Control   • Virtual Gauge Relocation

The system establishes an initial baseline gauge length (L₀) between selected reference coordinates and tracks their active separation distance as L(t) across consecutive frames to compute strain components:

• Engineering Strain (Cauchy): ε_eng = (L(t) - L₀) / L₀
• True Strain (Logarithmic): ε_true = ln(L(t) / L₀) = ln(1 + ε_eng)
• Transverse Strain & Poisson’s Ratio: ε_trans = (W(t) - W₀) / W₀, where ν = -(ε_trans / ε_axial)

Optical Tracking and Correlation Methods

The software architecture provides three distinct tracking methodologies to accommodate different material characteristics, surface preparations, and elongation profiles:

Pattern Recognition and Centroid Tracking

A pattern is defined as an isolated cluster of surface points that stands out from the surrounding background through gray-level contrast, similar to how constellations are identified by the arrangement of stars. The software establishes the geometric centroid of this cluster at starting coordinates (X₀, Y₀) and tracks its sub-pixel displacement (Δu, Δv) across active frames.

Sub-Pixel Digital Image Correlation

For high-stiffness metals, structural alloys, and rigid composites, the system tracks stochastic surface speckles by evaluating the Zero-Normalized Sum of Squared Differences (ZNSSD) correlation criterion:

Coupled with the Inverse Compositional Gauss-Newton (ICGN) algorithm and bi-cubic spline interpolation, the tracking engine resolves displacement increments down to 0.01 pixels. This provides spatial measurement resolutions better than 0.5 µm on the Quantum-1 and better than 0.2 µm on the Quantum-2.

Dynamic Reference Updating

During large-extension tensile tests on elastomers, flexible polymers, and rubber specimens stretching beyond 500% to 1000%, surface markers experience substantial physical distortion. 

When marker deformation exceeds the correlation confidence threshold or a portion of the pattern alters shape, the software automatically updates its reference template to the most recently detected pattern state. This dynamic re-anchoring maintains tracking continuity through sample rupture.

Silhouette Profile Tracking

For round bars, threaded fasteners, or specimens positioned inside high-temperature testing chambers where applied surface markings burn off, the system operates in silhouette mode. Using uniform back-lighting, the software extracts and tracks external specimen edges directly to calculate diameter contraction, necking profiles, and true cross-sectional area changes without surface preparation.

Optical Architecture and Active Lighting

Metrological precision depends on optical stability and isolation from ambient testing room variations:

Telecentric Optical Configuration

Standard optical lenses exhibit perspective magnification shifts when a specimen moves along the optical axis during grip seating or necking. Quantum telecentric lenses accept only light rays parallel to the optical axis. Magnification remains constant across the entire optical depth of field, eliminating pseudo-strain artifacts caused by out-of-plane specimen movement.

Dual Shortwave Active Illumination

Standard on all Quantum configurations, the integrated Dual Shortwave Light Array operates in tandem with optical bandpass filters:

• Ambient Light Rejection: Blocks 50/60 Hz laboratory lighting flicker, fluorescent cycles, and passing shadows.
• Thermal Emission Suppression: Neutralizes radiant red and infrared glow emitted by hot specimens inside testing furnaces.
• Motion Blur Elimination: High-intensity output allows sub-millisecond exposure times, preserving sharp boundary definition during dynamic high-speed tests up to 1000 Hz.

Multi-Vector Measurement Toolset

The Quantum software integrates four distinct measurement tools within a unified optical system:

 [ Tool #1: Deflection ]          [ Tool #2: Axial Extensometer ]
         ▲                                   ┌───┐ Marker A
         │ Single-Point Deflection           │   │
   ══════●══════                             │ ▲ │ 
         │ (Midspan Position)                │ │ │ ΔL (Gauge Length L0)
         ▼                                   │ ▼ │
                                             │   │
                                             └───┘ Marker B

 [ Tool #3: Free Parallel Length ]  [ Tool #4: Transverse & Width ]
         ┌───┐                               ┌───┐
     ┌───┼───┼───┐ Top Parallel Limit    ┌───┼───┼───┐
     │   │   │   │                       │ ◄─┼ W0┼─► │ Width Contraction
     │   │   │   │ Le (Parallel Span)    │   │   │   │ (Poisson's Ratio /
     │   │ * │   │ Fracture Verification │ ◄─┼W(t)─► │  r-value / Area)
     └───┼───┼───┘ Bottom Parallel Limit └───┼───┼───┘
         └───┘                               └───┘

• Tool #1: Single-Point Displacement (Deflection / Stroke): Tracks vertical or horizontal displacement of a single coordinate point for flexural beam tests (ASTM D790, ISO 178), shear lap joints, and compression platens.
• Tool #2: Two-Point Axial Tracking (Conventional Extensometer): Replaces mechanical clip-on gauges by tracking axial separation (L₀) to calculate Young’s Modulus (E), offset yield strength (R_p0.2), and total elongation at break (A) per ASTM E8/E8M and ISO 6892-1.
• Tool #3: Full Free Length / Parallel Length Tracking (L_e): Evaluates deformation along the entire parallel length of the specimen, identifying localized necking and verifying whether fracture occurred within valid gauge boundaries (L_e).
• Tool #4: Transverse Strain Measurement (Width & Diameter): Included on the Quantum-2, this tool measures continuous lateral contraction across multiple parallel vectors to compute Poisson’s ratio (ν, ASTM E132), plastic strain ratio (r-value, ASTM E517 / ISO 10113), and true cross-sectional area reduction.

Post-Test Data Re-Analysis

The Quantum Series records uncompressed, full-frame image sequences synchronized with load-cell channels throughout the test. Because the visual history is preserved, gauge parameters can be re-evaluated post-fracture without re-running physical specimens:

Test Execution ──> Synchronized Image Recording ──> Test Completion
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┌──────────────────────────────────────────────────────────┘
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[ Post-Test Re-Analysis Workspace ]
├── Relocate axial gauge points directly over the fracture zone
├── Add multiple virtual transverse lines to compute r-values
├── Adjust gauge lengths (e.g., convert 50 mm L0 to 25 mm L0)
└── Re-export verified stress-strain datasets without re-testing

• Relocate Gauge Positions: Position virtual gauge marks directly over the necking zone to extract true post-yield elongation (A_u) if a sample breaks outside the original center.
• Adjust Baseline Gauge Length (L₀): Convert baseline gauge spans (e.g., switching from 50 mm to 25 mm L₀) post-test.
• Insert Transverse Vectors: Add new transverse measurement lines across specific cross-sections post-test to evaluate localized necking geometry.

Testing Machine Integration and Control

The Quantum Series connects directly to Universal Testing Machines (UTMs) and laboratory data acquisition networks via integrated hardware interfaces:

• Closed-Loop Strain Regulation: Low-latency analog output (±10V, 16-bit) supplies real-time strain feedback directly to the UTM controller for ISO 6892-1 Method A1 and ASTM E8 Method A closed-loop strain-rate control.
• Digital Communication: Live measurement streams export via USB 3.0, serial communication ports, or TCP/IP network protocols.
• Analog & Digital Input: Accepts external load, position, and temperature signals for fully synchronized multi-channel evaluation.
• Dynamic Acquisition Rates: Frame rates up to 1000 Hz support high-rate tensile evaluations, component drop tests, and cyclic fatigue testing.

Technical Specifications by Model Variant

International Standards Compliance

• Extensometer Calibration: ISO 9513 (Class 0.5 and Class 0.2), ASTM E83 (Class A, Class B-1, Class 0.5).
• Metallic Materials Testing: ISO 6892-1 / ISO 6892-2 (Method A1 closed-loop strain regulation), ASTM E8 / ASTM E8M, ASTM E517 / ISO 10113 (Plastic strain ratio r-value), ASTM E132 / ASTM E111 (Poisson’s Ratio and Young’s Modulus).
• Polymers, Rubbers & Composites: ISO 527-1 / -2, ASTM D638, ASTM D412, ISO 37, ASTM D3039, ISO 527-4 / -5, ASTM D790, ISO 178.