High Temperature, Low Strain, Extended Performance Capacitive Extensometers (1200°C or 1600°C) – Model 7650A

High precision extensometer measures axial strains on specimens at temperatures up to 1600 °C (2900 °F). Compatible with materials testing furnaces or induction heating. May be used for strain-controlled, high frequency fatigue tests. 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.

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


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


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

Model 7650A extensometers measure strains with extremely high precision due to their design features and low strain range. All models are capable of tension and compression strain measurement, and may be used for fatigue testing under fully reversed load and strain conditions at frequencies up to 10 Hz.

All 7650A 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 provide high accuracy, high resolution measurements and perform high temperature fatigue testing at the highest possible frequencies. 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 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 7650A is often customized for specific test needs. Contact Epsilon for a configuration that matches your requirement.

Download Data Sheet

  • May be left on through specimen failure.
  • 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. Rod lengths >250 mm (10″) can affect the final class rating.

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

Hysteresis: ≤0.1% FS typical

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 cable

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

Coolant Interface: Two barbed hose fittings for 1/8” (3.2 mm) ID coolant hoses

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 (size: 190 mm L x 130 mm W x 180 mm H; weight: 3.5kg; power: 100-240VAC, 200W)
    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
  • Load frame mounting brackets
  • Connectors to interface to nearly any brand of test equipment
  • Bulkhead adapters for use in vacuum chambers
  • Connectors to interface to nearly any brand of test equipment
  • Rod tips can be straight chisels or conical tips; specify when ordering

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 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:  7650A_ _ _ __ _ __ _
Model Number:
7650A_ _ _ __ _ __ _
Ceramic rod lengths are made to fit furnaces as required. Provide furnace dimensions and electrical outlet type at time of ordering.

Requires external mounting brackets and 110 – 240VAC / 4W electrical power. Water cooling is recommended; required for 1000 °C and above.

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

Example: 7650A-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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