3549 High Temperature Hot Mountable Furnace Extensometers (1200 °C or 1600 °C) for Elevated Temperature Axial Testing

The 3549 high temperature hot mountable furnace extensometers from Epsilon can be connected to the test sample in a few seconds. This hot mountable unit has very low sensitivity to vibrations, making it perfect for the demanding requirements of high temperature, strain controlled axial testing, and other ordinary test methods.

  • Operation of Model 3549, and all other Epsilon’s extensometers, is verified to appropriate standards such as ISO 9513 or ASTM E83 with in-house calibration systems that are calibrated with Epsilon’s laser interferometer system
  • Epsilon extensometers can be used with virtually every brand of test equipment and provided with the appropriate connected to plug in directly, or provided with a separate amplifier and conditioner
  • With 20+ year history of service to the materials testing community, Epsilons stands behind its products to meet the critical application needs of customers

The Model 3549 is a major breakthrough in the design of externally mounted furnace extensometers. This new extensometer is designed to meet the strict demand of strain controlled testing as given in ISO 6892, while bringing in a number of innovative features that will help to enhance productivity with static testing applications, like compression and tension testing, and long term testing, such as creep and low cycle fatigue.

The overall design reduces any influence from common lab environment vibrations. This hot mountable unit also includes a novel feature that enables users to accurately fix the contact force against the test specimen. This enables an even and repeatable contact force, restricting contact force-induced errors.

The extensometer is mounted on slide bracket, which can be attached to the load frame of the test system; optional load frame mounting brackets are also offered. Its gauge length is automatically set before mounting on the test specimen, which enables hot mounting after reaching a thermal equilibrium.

The Model 3549 standard temperature version is designed for use in split type materials testing furnaces to 1200 °C (2200 °F) and comprises of water-cooled bracketry. The high temperature option enables temperatures up to 1600 °C (2900 °F). The extensometers can be put to use in carousel systems for quick high temperature testing.

The standard temperature version (to 1200 °C) is provided with high purity alumina rods. The high temperature instrument includes alpha grade silicon carbide rods. Rods are customized to suit the length required for furnace. Customers can integrate mounting brackets with the furnace cut-out. Load frame mounting brackets can also be provided by Epsilon to fit the test frame.

The Model 3549 hot mountable furnace extensometers are strain gaged devices and they can be used with any electronics developed for strain gaged transducers. They are most often linked to a test machine controller. The signal conditioning electronics for the extensometer is normally included along with the test machine controller, or may be added.

In this case, the extensometer is distributed along with the correct connector and wiring for direct plugging into the electronics. For systems that lack the needed electronics, Epsilon can offer a range of solutions, enabling the extensometer output to be connected to chart recorders, data acquisition board, or other equipment.


The key features of the 3549 high temperature hot mountable furnace extensometers are as follows:

  • Hot mountable and retractable.
  • Developed for those applications that need greater than ±2.5 mm (±0.10”) full scale measuring range. For applications that need smaller full scale ranges, customers can see Model 3648 or Model 7650A.
  • May be left on through specimen failure.
  • The gauge length is automatically set between each test with Epsilon’s innovative auto-setting mechanism that enables the device to be mounted to the sample in seconds.
  • Developed to meet the demands of strain controlled testing, such as required by ISO 6892, and also more common testing. The Model 3549 is able to isolate the strain sensing components from external vibrations.
  • Innovative slide mount enables the extensometer to engage the specimen after achieving the test temperature.
  • Includes contact force setting assembly to easily control the contact force, enabling easy and repeatable placement of the extenso¬meter on subsequent specimens using the same amount of force.
  • The gauge length can be easily adjusted to almost any gauge length using gauge length spacers.
  • Rugged, dual flexure design for improved strength and performance.
  • All models can measure in both compression and tension and can be used for cyclic testing.
  • Most standard units meet the requirements of ASTM class B-1 for accuracy. A test certificate is also included. ISO 9513 class 0,5 test certificates are available on request. Rod length configurations may impact the final class rating.
  • Full bridge, 350 Ω strain gaged design for compatibility with almost any test system.
  • Includes quick attach connectors for the water cooling lines and the electrical connections enables easy installation of the extensometer body.
  • Mechanical overtravel stops in both directions.
  • Includes high quality foam lined case and a spare set of ceramic rods.
  • Designed to be used in carousel systems or with single furnaces.
  • All units come with either alpha grade silicon carbide rods (1600 °C) or high purity alumina ceramic rods (1200 °C).


The main specifications of the 3549 high temperature hot mountable furnace extensometers are as follows:

  • Excitation: 5 to 10 VDC recommended, 12 VDC or VAC max.
  • Linearity: ≤0.15% of full scale measuring range, depending on model
  • Output: 1.5 to 2 mV/V, nominal, depending on model
  • Contact Force: Adjustable up to 400 g
  • Operating Force: <30 g typical
  • 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
  • CE certified


The optional accessories for the 3549 high temperature hot mountable furnace extensometers are as follows:

  • Model 2050 constant temperature water re-circulating bath
  • Shunt calibration
  • Load frame mounting brackets
  • Connectors to interface to almost any brand test equipment
  • High temperature option (-HT suffix) for use to 1600 °C
  • Specify rod tip style desired. Available choice are: Vee chisel, straight chisel, conical tip
  • Specialty knife edges
Hot-mountable extensometer for high-temperature strain measurement (Epsilon Technology - Model 3549)

3549 High Temperature Hot Mountable Furnace Extensometers (1200°C or 1600°C) for Elevated Temperature Axial Testing


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