Strain gauge extensometer 3742

high-temperatureclip-ontensile

Overview
At STEP Lab, we are official distributors of Epsilon products and offer a wide range of high-accuracy extensometers for industrial and laboratory testing. Epsilon extensometers measure specimen deformation for strain and tensile testing across many applications. Solutions include both contact (clip-on/long-arm) and non-contact (optical) systems designed to meet industry standards and laboratory requirements.

Types of extensometers

• Contact extensometers: Clip-on and long-arm designs that attach to the specimen. Common for routine testing, economical and suited to relatively rigid samples. Available in manual, semi-automatic and fully automated configurations; some models support elevated or low-temperature use.
• Non-contact (optical) extensometers: Camera- or laser-based systems that measure strain without touching the specimen. Ideal for sensitive or high-elongation materials and for tests where contact would affect results. Example: the Epsilon ONE, offering high accuracy, real-time operation at high sample rates and wide temperature compatibility.

Latest model highlighted
New Automatic Gauge Length Extensometer – Model 3742
The Model 3742 is a clip-on extensometer with automatic gauge length setting designed for fast, repeatable mounting without gauge pins. It features a Quick-Swap system to change gauge lengths in seconds without tools, delivering high precision and productivity for laboratories with frequent specimen or gauge-length variations.

Model 3742 — Features

• Automatic gauge length: gauge length set automatically when mounted on the specimen; no gauge pins required.
• Quick-Swap system: change gauge lengths in seconds without tools.
• Fine-adjust feature for quick gauge-length tuning.
• Clamping force adjustable without tools.
• Can remain mounted through specimen failure in most applications.
• Suitable for tension and compression testing, including cyclic and closed-loop strain control.
• Quick Attach Kit for fast specimen mounting.
• Rugged dual-flexure design for higher-frequency cyclic tests.
• Mechanical over-travel stops in both directions.
• Hardened tool steel knife edges, replaceable; spare set of standard and 3-point knife edges included.
• High and low temperature options (wide ranges available).
• 350 ohm full-bridge strain gage design for compatibility with most test systems.
• Epsilon Shunt Calibration System included for on-site electrical calibration.
• Supplied with foam-lined carrying case.

Contact extensometers — key points
Contact extensometers are engineered for repeatable performance in many test conditions, with outputs and accuracy designed to meet ASTM/ISO standards. Typical highlights include full‑bridge 350 ohm strain gauges, suitability for tension and compression, robust double-bending designs, remote temperature options and quick-attach kits for multiple specimen sizes.

Non-contact extensometers — key points
Optical extensometers provide always-on, real-time measurement with high tracking rates (hundreds to thousands of Hz), laser-assisted alignment, telecentric optics to reduce errors from out-of-plane motion, selectable filters/optical settings and flexible analog/digital outputs. They support many ISO and ASTM standards and are factory calibrated.

Key factors in the choice of extensometer

• Characteristics of materials and specimens: expected deformation range, sensitivity requirements, fracture behaviour, and sample geometry.
• Test requirements: test type (tensile, compression, bending, cyclic), required gauge length (standards may dictate choice), and accuracy/certification needs (ISO/ASTM).
• Test environment: temperature extremes, dust, vibration or air currents—environmental factors that may favour contact or robust non-contact models.

Comparison table (contact vs non-contact)
Application | Contact extensometers | Non-contact extensometers
Application: Economical solution for standard applications | Easily adaptable to different test applications
Specimen: Inherently rigid samples | All, including sensitive samples and those with high breaking energy
Temperature: Up to 100 °C (typical for many contact models) | Typical optical limits around ambient/controlled conditions depending on package
Operation: Manual (typical) | Automatic: high reproducibility and reduced operator influence

Technical characteristics / specifications

• Power supply: recommended 5–10 VDC (max 12 VDC/AC) for contact extensometers; non-contact systems use their own 100–240 VAC supply depending on model.
• Output: contact units typically 2–4 mV/V nominal (model dependent); non-contact systems provide ±10 V analog and digital outputs (high-resolution digital outputs available).
• Accuracy: contact models meet ASTM E83 class B‑1 (for gauge lengths ≥20 mm) and ISO 9513 class 0.5 in standard configurations; optical units can achieve ISO 9513 class 0.5 and ASTM E83 B‑1 or better at appropriate gauge lengths.
• Linearity: ≤0.15% of full scale (typical for many contact models).
• Temperature ranges: standard contact ranges −40 °C to +100 °C, with available high/low temperature options (some options cover cryogenic to +200 °C); optical systems specified per optical package and environmental limits.
• Cable: integrated ultra-flexible cable (standard ~2.5 m / 8 ft for many contact models).
• Specimen sizes & attachments: quick-attach kits/wireforms for round specimens Ø 2–25 mm and flats up to 12 × 31 mm (typical); other attachments available for different geometries.
• Operating force: depends on configuration; typical clip-on ranges are low (<1 N); exact values depend on model and options.
• Resolution & rates (optical): quasi-static resolution <0.5 µm, dynamic resolution <2.5 µm (typical); real-time data rates 300–3000 Hz (package dependent).
• Maximum elongation & tracking: optical systems can track very large elongations (subject to field of view) and high tracking speeds (e.g., >1500 mm/s) for dynamic tests.