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High Temperature Axial/Torsional Extensometers (1200°C or 1600°C) – Model 7650

Simultaneously measures axial and torsional strains at high temperatures on specimens tested in axial/torsional 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.

Gauge Lengths:

12.5 – 25 mm

Measuring Ranges:

+2.5 mm / -0.5 mm axial and ±1° torsional typical

Temperature Range:

Ambient to 1600 °C with -HT option

Key Features:

Hot-mountable, axial-torsional furnace extensometer

Tel: +86-531-86510531Ext.9

Fax: +86-531-86510535

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Model 7650 extensometers are primarily used on round specimens tested in bi-axial test machines capable of simultaneous axial and torsional loading. 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 7650 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 minimize 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 water-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 7650 is often customized for specific test needs. Contact Epsilon for a configuration that matches your requirement.
  • 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.
  • Standard units meet ASTM class B-1 requirements for accuracy (axial). A test certificate is included. ISO 9513 class 0,5 test certificates are available upon request.
  • 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.

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


11 point digital linearization, ≤0.1% FS typical linearity (axial and torsional)


≤0.1% FS typical


≤0.2% FS typical at ±1° shear with 25 mm diameter specimen and 12.5 mm gauge length


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


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

Sensor Cables:

2m (6.5 ft) room temperature cables

Output Cables:

Flexible 2.4 m (8 ft) analog output cables

Specimen Size Range:

Fits most round specimen diameters

Test Frame Layout:

Accommodates test frames with torsional actuator located above or below specimen

Operating Force:

<30 grams typical

Contact Force:

<560 grams typical


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


Includes power supply for your country
  • High temperature option (-HT suffix) for use to 1600°C
  • Load frame mounting brackets
  • Bulkhead adapters for use in vacuum chambers
  • Model 2050 constant temperature water re-circulating bath
  • Connectors to interface to nearly any brand test equipment
  • See Epsilon’s Axial/Torsional Extensometer Calibrator
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