3448 High Temperature Self-Supporting Furnace Extensometers (1200 °C) for Furnaces and Induction Heating Systems

Epsilon’s 3448 high temperature extensometers have been designed for use with induction heating systems and furnaces. These units use the company’s exclusive, self-supporting design, and a wide variety of options are available to cover most testing applications.

  • In 1995, Epsilon introduced the first self-supporting, axial furnace extensometer with ceramic fiber cords to the market
  • Epsilon’s engineers have evaluated cord positions in both the induction heater version (rods and fiber cord attachments parallel to one another) and the conventional ceramic fiber cord attachments (elevated above the ceramic rods), and found their performance to be same
  • All Epsilon’s extensometers are verified to applicable standards such as ISO 9513 or ASTM E83 using in-house calibration system that are calibrated with Epsilon’s laser interferometer system
  • Providing more than 20 years of service to the materials testing community, Epsilon stands behind its products to meet the critical application requirements of users

This unique high-temperature extensometer has been developed by Epsilon to test ceramics, composites, and metals at the high temperatures produced by induction heating systems and furnaces. A combination of features makes these extensometers easy to use and improves performance compared to other similar high temperature extensometers.

Light, flexible ceramic fiber cords are used to position the units on the specimen, making this extensometer self-supporting on the specimen. There is no requirement for furnace mounting brackets. The side load on the test sample is significantly reduced due to the light weight and self-supporting design of the sensor.

A Model 3448 are easily accepted by most furnaces that have a side cut-out for an extensometer. A different ceramic cord placement enables the extensometer to easily pass between the coils for induction heating systems.

The  combination of convection cooling fins and radiant heat shields allow Model 3448 to be used at specimen temperatures up to 1200 °C (2200 °F) without any cooling. An optional tiny air fan improves stability at the highest temperatures and can be used to acquire high accuracy and for tests with small elongations.

The fan has a magnetic base for support, so it can be positioned at any locations close to the extensometer. For induction heated systems, fan cooling is generally not required.

The extensometer also comes with high purity alumina ceramic rods that are available in customized lengths to fit the furnace. Every extensometer includes a spare set. Customers can specify vee chisel, straight chisel, or conical contact points, as desired.

Most units function equally well in compression and tension, making it possible to perform compression, tensile, and cyclic tests such as low cycle fatigue with a single unit.

Special models are available for vacuum furnaces. Epsilon can also offer a radiant heat transfer-cooled version. This requires that the extensometer module is surrounded by a water-cooled enclosure having a front slot for the ceramic rods.


The key features of the 3448 high temperature extensometers are as follows:

  • May be left on through specimen failure.
  • Rugged, dual flexure design facilitates improved strength and performance.
  • Full bridge, 350 ohm strain gaged design provides compatibility with nearly any test system.
  • All units have high purity alumina ceramic rods
  • Mechanical overtravel stops in both directions.
  • It can be mounted with flexible ceramic fiber cords. Easy to install, the Epsilon exclusive design prevents the requirement for external support brackets. Low contact force does not differ during testing like certain externally supported extensometers.
  • Includes high-quality, foam-lined case, eight ceramic fiber cords and a spare set of ceramic rods.
  • Most standard units meet the requirements of ASTM class B-1 for accuracy. A test certificate is included. ISO 9513 class 0,5 test certificates are available on request. Rod length configurations can impact the final class rating.
  • Use without cooling to 1200 °C (2200 °F). Optional small fan enhances stability at highest temperatures.
  • It can be used on nearly any furnace with side entry cut-out for extensometers. Alternate configuration is available for insertion between coils of induction heaters.
  • Versions available for use in controlled and vacuum atmospheres. Radiant heat transfer cooled versions are also available for these applications.


The main specifications of the 3448 high temperature extensometers are as follows:

  • Output: 2 to 4 mV/V, nominal, depending on model
  • Excitation: 5 to 10 VDC recommended, 12 VDC or VAC max.
  • Temperature Range: Ambient to 1200 °C max (2200 °F), all versions
  • Linearity: ≤0.15% of full scale measuring range, depending on model
  • Operating Force: 10 to 20 g typical
  • Contact Force: Adjustable, approximately 200 g depending on configuration
  • Cable: Integral, ultra-flexible cable, 2.5 m (8 ft) standard


The following options are available with the 3448 high temperature extensometers:

  • Shunt Calibration
  • Ceramic cord orientation for furnaces or induction heaters (specify)
  • Air cooling fan, add suffix -AC
  • Specify rod tip style desired. Available choice are: Straight chisel, Vee chisel, Conical tip

3448 High Temperature Self-Supporting Furnace Extensometers (1200°C) for Furnaces and Induction Heating Systems


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