Precision Optical Extensometers – Epsilon ONE®

Precision Optical Extensometers – Epsilon ONE® Features

Epsilon ONE® optical non-contact extensometers perform high-accuracy, high-resolution, non-contacting axial strain and displacement measurement. These extensometers are suitable for testing high-modulus materials such as metals and composites, high-elongation materials, thin or delicate specimens, cyclic fatigue, strain controlled testing, deflectometer applications, and measuring crack opening displacements. Strain or extension is measured and output in real time.

Epsilon ONE’s high resolution and ISO 0,5 / ASTM B-1 accuracy classes make it suitable for non-contact measurement of a wide range of strain values, from very small strains required to measure modulus* of metals, composites, ceramics and CMCs through elastomers and everything in between.

Class-leading accuracy and resolution are achieved by Epsilon’s comprehensive optical path optimization, a unification of several optical technologies and signal processing algorithms. Ultra-high camera resolution, real-time data rates up to 3000 Hz, minimization of optical error sources, and signal processing techniques provide high strain resolution and accuracy with the lowest noise. No other system on the market combines all of these technologies.

The Laser-Assist Alignment System provides an instant alignment and distance spot check. Epsilon ONE will project pre-aligned laser lines on the specimen before the test, revealing any misalignment. During the test, high precision telecentric lenses on the PT models eliminate errors due to out-of-plane movements – a common source of errors for many video extensometers. Epsilon ONE arrives factory calibrated – there are no calibration grids or gauge length bars, saving a great deal of time.

The system sets up for new specimen types in minutes and requires very little training or skill to use. The desktop user interface software and optional Touch Interface provide continuous digital readouts and status information.

Epsilon ONE was designed for the fastest specimen cycle times. Auto-start repetitive tests without any software interaction; Epsilon ONE is always running, and its Instant Reset and Automatic Mark Detection eliminate software start/stop interactions common with video extensometers.

Epsilon ONE provides a calibrated ±10V strain signal as an input for the testing machine’s controller. The extensometer fits all types of materials testing machines, including machines that have an environmental chamber with a window (contact Epsilon for fitment).

*As with clip-on extensometers, accurate measurement of modulus requires a well-aligned load train and grips, and symmetrical specimens that are centered in the grips. Gauge lengths ≥25 mm are recommended in most cases. Contact Epsilon for additional Best Practices.

Precision Optical Extensometers – Epsilon ONE®

• Always on, always ready: Unlike DIC systems, software interactions are unnecessary when running repetitive tests.
• Always real-time: Post-processing is never required, even at the highest data rates.
• Faster throughput with Instant Reset: Auto-start repetitive tests without touching the extensometer or software.
• Reliable, automatic mark detection: Robust tracking of bright or dark marks beyond 1000% strain and speeds >1500 mm/second.
• Laser Assist Alignment System: Provides an instant visual spot-check for specimen alignment and optics positioning.
• Precision Telecentric Design: Epsilon ONE’s telecentric lenses prevent common sources of error – Read this Tech Note.
• Fully factory calibrated: Epsilon calibrates using the industry’s most comprehensive process to account for scaling, skew, lens distortion, and uneven lighting. A2LA accredited factory calibration, traceable to the SI; no grids or bars are required for calibration.
• Cleaner workspace: No need for an additional computer and monitor; the included User Interface software has very low resource requirements and can run on the test machine’s computer.
• Optional Touch Interface: Access and control the Epsilon ONE without a computer. (see a demo )
• Retractable high-stiffness mounting: Industry-leading ease-of-use while maintaining maximum dynamic range and vibration rejection.
• Selectable multi-line specimen marking: Automatically identify and report the region of highest strain concentration, in real time.
• Wide range of selectable filter and optical settings enable high performance with many different materials and specimens.
• Faster Testing: Save time with industry-leading 200+ Hz dynamic range and automatic gain compensation filters.
• Admin/User Modes: Define, save and reload settings for specific specimens and test methods, then lock them in User Mode.
• Real-time digital output: High-speed data stream including APIs for control and status, and examples for automation and integration.
• Better Strain Control: Built-in high speed 16-bit analog output; not susceptible to unpredictable cyclic bias errors typical of DIC systems.
• Versatile Output Modes: output ±10V as % Strain, Length (mm), or Elongation (mm).
• Strain Metrics: Report strain measures using five finite or small strain theories.
• Applicable for testing with many ISO and ASTM standards, including:
  • ISO 6892-1, 527-2, 527-4, 527-5
  • ASTM E8, E9, D3039, D638, A370, D3552, E646
• Turn-key: Each base package includes
  • Optics Package with laser-assist alignment system
  • Lighting Module
  • Sensor Controller
  • Mounting Interface Subassembly
  • Specimen Marking Kit
  • Cables and software
• Includes high quality foam lined case.
• Patented.

Key Applications

• Testing of high-modulus materials – resolution and accuracy for very small strain measurements typical with these materials
• Automated testing – no software interaction is required between repetitive tests
• Fine / thin specimens – <Ø20 μm (0.001”) specimens
• Elastomers and high-elongation plastics – best-in-class performance; >1000% strain and  >1.5 meters/second tracking speed
• High speed cyclic testing – test frequencies up to 100 Hz and real time data rate up to 3000 Hz
• Long-term creep testing – excellent thermal stability and automatic recovery in the event of a test interruption