Extensometers for materials testing

High Temperature XY Planar Biaxial Extensometer (1200°C or 1600°C) – Model 7651

Simultaneously measures in-plane bi-axial strains at high temperatures on specimens tested in X-Y bi-axial machines. For use with materials testing furnaces or induction heating up to 1600 °C (2900 °F). May be used for bi-axial strain controlled fatigue. Slide mounting system enables mounting to hot specimens in seconds.
Epsilon extensometers are COMPATIBLE WITH VIRTUALLY EVERY BRAND OF TEST EQUIPMENT and can be supplied with the correct connector to plug in directly.

to the materials testing community, you know we will be there to stand behind our products when your critical application requires it.

Operation of these, and all of Epsilon’s extensometers, are


using in-house calibration systems that are calibrated with Epsilon’s laser interferometer system.

Model 7651 extensometers measure combined in-plane strains in flat cruciform specimens tested in machines capable of simultaneous X and Y (perpendicular) axial loading and on standard flat samples tested in pure tension. All models are capable of bi-directional displacement in both axes and may be used for strain-controlled fatigue testing under fully reversed load and strain conditions at frequencies up to 10 Hz.

All 7651 models mount rigidly on the load frame and incorporate slide mounting to bring the extensometer into contact with the specimen. The gauge length is set automatically before mounting on the test specimen, which allows for hot mounting after thermal equilibrium has been reached.

These units are specifically designed to eliminate crosstalk between axes and to provide high accuracy, high resolution measurements. They incorporate capacitive sensors for low operating force and include electronics with programmable filtering and multi-point linearization for improved performance and accuracy. The overall design minimizes, and in many cases virtually eliminates, any influence from common lab environment vibrations.

These liquid-cooled extensometers are equipped with high purity alumina rods with conical rod tips for specimen contact when testing to 1200 °C (2200 °F). Silicon carbide rods are used for the 1600 °C (2900 °F) high temperature option.

The Model 7651 is often customized for specific test needs. Contact Epsilon for a configuration that matches your requirement.

Download Data Sheet

  • Hot mountable and retractable.
  • Self-setting gauge length with fine adjustment feature.
  • All models can measure in both tension and compression and may be used for cyclic testing at test frequencies up to 10 Hz.
  • Ships fully calibrated with calibration that is traceable to NPL; voltage output may be user-specified (typically 0-10V).
  • Excellent ambient vibration rejection; primary vibration mode >100 Hz typical
  • Digital controller and power supply included. Provides high level DC voltage output with low noise. Easily interfaced to test controllers, data acquisition boards and chart recorders.
  • Includes high speed analog and digital outputs.
  • Web-based user interface for setup and data acquisition.
  • Selectable analog and digital filter options from 2 Hz to 3 kHz.
  • Built-in calibration reference and auto-zero features.
  • Multiple extensometer calibration files may be loaded for use with one controller.
  • Can be used with specimens at elevated temperatures while only requiring room temperature calibration.
  • Quick-disconnect liquid cooling fittings and signal cables.
  • Includes high quality foam lined case and a spare set of rods.

Download Data Sheet

Analog Output: User specified, ±10VDC typical, ±10.8VDC rail

Digital Output: 24 bit high speed Ethernet output with built-in web interface

Cyclic Testing: Up to 10 Hz, depending on test system and test amplitude

Accuracy: Standard configurations meet ASTM E83 class B-1 and ISO 9513 class 0,5 requirements for accuracy. A test certificate is included.

Linearity: 11 point digital linearization, ≤0.1% FS typical linearity

Hysteresis: ≤0.1% FS typical

Crosstalk: none

Resolution: <75 PPM (0.0075%FS) RMS @ 4 kHz, <6 PPM (0.0006%FS) @ 100 Hz at gauge length

Filter: Selectable 100 Hz analog and 2 Hz – 3 kHz digital filters

Sensor Cables: 2 m (6.5 ft) room temperature cables

Output Cables: Flexible 2.4 m (8 ft) analog output cables

Specimen Size Range: Fits any flat cruciform or axial-only test specimen with a test area larger than the extensometer GL

Operating Force: <30 grams typical

Contact Force: <560 grams typical

Environment: Recommended for testing in dry air, inert / non-corrosive gases, or vacuum

Power: Includes power supply for your country



Download Data Sheet

  • Model EPS170 constant-temperature recirculating chiller
    Liquid cooling is recommended for all elevated temperature tests to obtain the best measurement accuracy and retain the validity of a room temperature calibration when the specimen temperature is >540 °C (1000 °F). Cooling is necessary to prevent extensometer damage for testing in the range of ~800-1600 °C (1500-2900 °F). Epsilon Technology recommends the EPS170 constant-temperature recirculating chiller.
  • High temperature option (-HT suffix) for use to 1600°C
  • Bulkhead adapters for use in vacuum chambers
  • Load frame mounting brackets
  • Rod tips can be straight chisels or conical tips; specify when ordering
  • Connectors to interface to nearly any brand of test equipment

Download Data Sheet

Ordering Information

Click table options to configure

Gauge Length i
mm or inches #
12.5 mm -0125M 0125M
25.0 mm -025M 025M
0.500 in -0050 0050
1.000 in -0100 0100
Measuring Range (X & Y)¹ i
extension #
+1.5 / -1.5 mm -015M 015M
+2.0 / -1.0 mm -020M 020M
+2.5 / -0.5 mm -025M 025M
+0.060 / -0.060 in -060T 060T
+0.080 / -0.040 in -080T 080T
+0.100 / -0.020 in -100T 100T
Temperature Range
degrees #
Room temperature to 1200 °C (2200 °F) -ST ST
Room temperature to 1600 °C (2900 °F) -HT HT
Model Number:  7651_ _ _ __ _ __ _
Model Number:
7651_ _ _ __ _ __ _

Ceramic rod lengths are made to fit furnaces as required. Specify load frame configuration, loading axis orientation, furnace dimensions, and electrical outlet type at time of ordering.

Requires external mounting brackets and 110 – 240VAC / 4W electrical power. Liquid cooling is recommended; required for 800 °C and above.

Other configurations are available with special order; please contact Epsilon to discuss your requirements.

¹Consult factory for applications requiring different X and Y gauge lengths or measuring ranges.
Example: 7651-025M-020M-ST: 25 mm gauge length, +2.0 / -1.0 mm measuring range, standard temperature range (room temperature to 1200 °C)


If your unit is in need of service, calibration or repair, initiate the RMA process with us and we will be happy to assist.

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