Extensometers for materials testing

High Temperature Hot Mountable Furnace Extensometers (1200°C or 1600°C) – Model 3549

This model can be connected to the test sample in a few seconds. With very low sensitivity to vibrations, this hot mountable unit is ideal for the demanding requirements of strain controlled, elevated temperature axial testing and other common test methods.

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


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

Epsilon extensometers are COMPATIBLE WITH VIRTUALLY EVERY BRAND OF TEST EQUIPMENT and can be supplied with the correct connector to plug in directly, or supplied with a separate conditioner and amplifier.


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

The Model 3549 is a major advancement in the design of externally mounted, furnace extensometers. This new extensometer is designed to meet the stringent requirements of strain controlled testing as prescribed in ISO 6892, while introducing many new innovative features that help improve productivity with static testing applications (tension and compression testing) and long term testing such as low cycle fatigue and creep. The overall design reduces any influence from common lab environment vibrations. This unit also incorporates a new feature that allows the user to precisely set the contact force against the test specimen. This allows for even and repeatable contact force, limiting contact force induced errors. This extensometer mounts on a slide bracket (included) that can attach to the load frame of your test system; optional load frame mounting brackets are available. The gauge length for the 3549 is automatically set prior to mounting on the test specimen, which allows for hot mounting after thermal equilibrium has been reached.

The Model 3549 standard temperature version is made for use in split type materials testing furnaces to 1200 °C (2200 °F) and includes water-cooled bracketry. The high temperature option allows use to 1600 °C (2900 °F). These extensometers can be used in carousel systems for rapid high temperature testing.

The standard temperature version (to 1200 °C) is supplied with high purity alumina rods. The high temperature option is furnished with alpha grade silicon carbide rods. Rods are made to order to the length required for your furnace. Mounting brackets may be integrated with the furnace cut-out. Epsilon can also provide load frame mounting brackets to fit your test frame.

The Model 3549 extensometers are strain gaged devices, making them compatible with any electronics designed for strain gaged transducers. Most often they are connected to a test machine controller. The signal conditioning electron­ics for the extensometer is typically included with the test machine controller or may often be added. In this case the extensometer is shipped with the proper connector and wiring to plug directly into the electronics. For systems lacking the required electronics, Epsilon can provide a variety of solutions, allowing the extensometer output to be connected to data acquisition boards, chart recorders or other equipment.

Download Data Sheet

  • May be left on through specimen failure.
  • Hot mountable and retractable.
  • Designed for applications requiring greater than ±2.5 mm (±0.10 inches) full scale measuring range. For applications requiring smaller full scale ranges, please see Model 3648 or Model 7650A.
  • Designed to meet the demanding requirements of strain controlled testing, such as required by ISO 6892, as well as more common testing. The 3549 is designed to isolate the strain sensing components from external vibrations.
  • The gauge length is set automatically between each test with Epsilon’s unique auto-setting mechanism, which allows the device to be mounted to the sample in seconds.
  • The low contact force is easily controlled through the included contact force setting assembly. This allows for easy, repeatable placement of the extenso­meter on subsequent specimens with the same amount of force.
  • Innovative slide mount allows the extensometer to engage the specimen once the test temperature has been achieved.
  • All models can measure in both tension and compression and can be used for cyclic testing.
  • The gauge length of the 3549 can be easily adjusted to virtually any gauge length through the use of gauge length spacers.
  • The 3549 is designed to be used in carousel systems or with single furnaces.
  • Mechanical overtravel stops in both directions.
  • All units come with either high purity alumina ceramic rods (1200 °C) or alpha grade silicon carbide rods (1600 °C).
  • The 3549 includes quick attach connectors for the water cooling lines and the electrical connections, which allow for easy installation of the extensometer body.
  • Most standard units meet ASTM class B-1 requirements for accuracy. A test certificate is included. ISO 9513 class 0,5 test certificates are available upon request. Rod length configurations can affect the final class rating.
  • Includes the Epsilon Shunt Calibration System for on-site electrical calibration.
  • Rugged, dual flexure design for strength and improved performance.
  • Full bridge, 350 ohm strain gaged design for compatibility with nearly any test system.
  • Includes high quality foam lined case and a spare set of ceramic rods.

Download Data Sheet

Excitation: 5 to 10 VDC recommended, 12 VDC or VAC max.

Output: 1.5 to 2 mV/V, nominal, depending on model

Linearity: ≤0.15% of full scale measuring range, depending on model

Temperature Range: Standard (-ST) is to 1200 °C (2200 °F), optional (-HT) 1600 °C (2900 °F)

Cable: Integral, ultra-flexible cable, 2.5 m (8 ft) standard

Contact Force: Adjustable up to 400 g

Operating Force: <30 g typical



Download Data Sheet

  • Model 2050 constant temperature water re-circulating Bath
  • High temperature option (-HT suffix) for use to 1600°C
  • Load frame mounting brackets
  • Connectors to interface to nearly any brand of test equipment
  • Specify rod tip style desired; available choices are straight chisel, vee chisel, or conical tip

Download Data Sheet

Product Videos

Hot-mountable extensometer for high-temperature strain measurement

Extensometer for elevated temperatures – hot mount feature

Ordering Information

Click table options to configure

Gauge Length i

mm or inches #
10.0 mm -010M 010M
25.0 mm -025M 025M
50.0 mm -050M 050M
0.500 in -0050 0050
1.000 in -0100 0100
2.000 in -0200 0200

Measuring Range i

% strain #
±10% -010¹ 010
+20%/-10% -020 020
+50%/-10% -050 050
+100%/-10% -100² 100

Temperature Range

degrees #
Ambient to 1200 ˚C (Ambient to 2200 ˚F) -ST ST
Ambient to 1600 ˚C (Ambient to 2900 ˚F) -HT HT

Model Number:  3549_ _ _ __ _ __ _

Model Number:

3549_ _ _ __ _ __ _

Model 3542 Available Versions: Any combination of gauge length, measuring range and temperature range listed above is available, except as noted. Other configurations may be available with special order; please contact Epsilon to discuss your requirements.

¹Not available in 10 mm, 12.5 mm, or 0.5 inch gauge lengths.
²Not available in 50 mm or 2 inch gauge lengths.

Example: 3549-025M-050-HT: 25 mm gauge length,+50%/-10% measuring range, high temperature option (room temperature to 1600 °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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