High Temperature Self-Supporting Furnace Extensometers (1200 °C) – Model 3448

  • Epsilon developed this unique high temperature extensometer for testing metals, ceramics, and composites at the high temperatures produced by furnaces and induction heating systems. A combination of features make these extensometers easier to use and better in performance than other similar high temperature extensometers.

    The units are held on the specimen by light, flexible ceramic fiber cords. These make the extensometer self-supporting on the specimen. No furnace mounting brackets are required. The side load on the test sample is greatly reduced because of the self-supporting design and light weight of the sensor. Most materials testing furnaces with a side cut-out for an extensometer will readily accept a Model 3448. For induction heating systems, a different ceramic cord placement allows the extensometer to easily pass between the coils.

    The combination of radiant heat shields and convection cooling fins allow this model to be used at specimen temperatures up to 1200℃ (2200°F) without any cooling. An optional tiny air fan does enhance stability at the highest temperatures and is recommended for the highest accuracy and for tests with small elongations. The fan comes with a magnetic base for support so it can be mounted at any convenient location near the extensometer. Fan cooling is not generally needed for induction heated systems. High purity alumina ceramic rods are used. These are available in lengths as required to fit your furnace. A spare set is included with every extensometer. Specify chisel, vee chisel or conical contact points as desired.

    Most units operate equally well in tension and compression. Thus tensile, compression and cyclic tests like low cycle fatigue can all be performed with a single unit.

    For vacuum furnaces, special models are available. Epsilon can also provide a radiant heat transfer cooled version. This requires that the extensometer module be surrounded by a water cooled enclosure with a front slot for the ceramic rods.


  • • May be left on through specimen failure.

    • Full bridge, 350 ohm strain gaged design for compatibility with nearly any test system.

    • Mechanical overtravel stops in both directions.

    • 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.

    • All units come with high purity alumina ceramic rods.

    • Mount with flexible ceramic fiber cords. Very simple to install, this Epsilon exclusive design eliminates the need for external support brackets. Low contact force does not vary during testing like some externally supported extensometers.

    • Includes high quality foam lined case, a spare set of ceramic rods, and eight ceramic fiber cords.

    • Use without cooling to 1200℃ (2200°F). Optional small fan improves stability at highest temperatures.

    •Rugged, dual flexure design for strength and improved performance.

    •Versions available for use in vacuum and controlled atmospheres. Radiant heat transfer cooled versions are available for these applications.

    •May be used on nearly any furnace with side entry cut-out for extensometers. Alternate configuration available for insertion between coils of induction heaters. 


  • Air cooling fan, add suffix -AC

    Ceramic cord orientation for furnaces or induction heaters (specify)

    Specify rod tip style desired. Available choice are:

    Straight chisel, vee chisel, conical tip

    Shunt calibration module 


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

    Output: 2 to 4 mV/V, nominal, depending on model

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

    Temperature Range: Ambient to 1200℃ max (2200°F), all versions

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

    Contact Force: Adjustable, approximately 200 g depending on configuration

    Operating Force: 10 to 20 g typical 


Designed for use with furnaces and induction heating systems, these extensometers use Epsilon’s exclusive, self-supporting design. A wide range of options cover most testing applications.
Gauge Lengths:
10-50 mm
Measuring Ranges:
5%-100%
Temperature Range:
Ambient to 1200℃
Key Features:
Self-supporting furnace extensometer