Extensometers for materials testing

Rugged, Long Gauge Length Extensometers – Model 3543

This model is available in gauge lengths from 50 mm (2 inches) and larger, with measuring ranges up to 100 mm (4 inches). The unique design separates into two halves and the extensometer may be left on through specimen failure. These extensometers are widely used where long samples are required. They are ideal for testing steel re-bar, weld joints, and wire materials.

Epsilon designed and built the world’s first fully separable, strain gaged axial extensometer.

Model 3543 has over a decade of proven performance in the harshest testing environments.

Provides the necessary performance to successfully record strain on some of the most mechanically demanding specimens.

For applications where the ruggedness of the extensometer is crucial, the model 3543 has proven itself time-and-time again.


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

With over 15 years of proven reliability in the world’s most demanding testing environments, Model 3543 extensometer is designed to survive in those applications where standard axial extensometers would not. Designed by Epsilon, the Model 3543 was created to survive specimen failure by separating into two halves, thus preventing permanent damage to the module body. During operation, the upper half of the extensometer pulls out of the main body. Tapered measuring beams activate strain gaged flexures within the unit. This unique design allows long measuring ranges, yet retains compatibility with electronics for strain gaged transducers. These models offer high accuracy and are light weight but rugged, with low operating force. They are tension only units.

The units have hardened tool steel knife edges. Standard quick attach wires provided with the extensometer work on flat specimens up to 12 x 31 mm (0.5 x 1.25 inch) and on rounds up to 25 mm (1 inch) diameter. Optional quick attach kit wire forms are available for use on larger samples. See Model 3542L for long gauge lengths with smaller measuring ranges.

The Model 3543 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

  • Specifically designed to withstand testing through failure for specimens with rough or non-uniform surfaces such as rebar.
  • The unit is designed so that the two halves of the extensometer come apart to prevent damage at specimen failure.
  • Designed for non-reversed tension only testing. This model is not intended for strain control, cyclic or compressive testing.
  • Full bridge, 350 ohm strain gaged design for compatibility with nearly any test system.
  • All standard units meet ASTM class B-2 requirements for accuracy. Suitable for measuring plastic deformation and elongation to failure. For modulus and yield strain, a 3542 is required.
  • Rugged design for reliable testing.
  • Standard quick attach kit for quick mounting to specimens.
  • Hardened tool steel knife edges are easily replaced. A spare set comes with every extensometer.
  • High temperature options extend operation to +150 °C (300 °F).
  • Replaceable arms and spacers for ease of repair. The optional gauge length spacers allow the gauge length of the extensometer to be easily increased for different testing requirements.
  • Includes the Epsilon Shunt Calibration System for on-site electrical calibration.
  • Includes high quality foam lined case.

Download Data Sheet

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

Temperature Range: Standard (-ST) is -40 °C to +100 °C (-40 °F to 210 °F)

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

Standard Quick Attach Kit: Fits round samples up to 25 mm (1.0 inch) diameter and flats to 12 mm thick by 31 mm wide (0.5 inch by 1.25 inch)

Operating Force: 125 g typical



Download Data Sheet

  • Quick attach kit wireforms for large specimens
  • Spacers to change gauge lengths
  • Connectors to interface to nearly any brand of test equipment
  • A twist option is available for use in applications where specimen twisting greater than 3° is expected. The 3543TW option can accommodate up to 15° of twist.
  • Geotextile clamps are an option for testing fabric and mesh specimens up to 200 mm wide – 3543GT
  • Specialty Knife Edges

Download Data Sheet

Product Videos


Rebar testing through failure using a rugged extensometer


Ordering Information

Click table options to configure

Gauge Length i

mm or inches #
50.0 mm -050M 050M
100.0 mm -100M 100M
150.0 mm -150M 150M
200.0 mm -200M 200M
250.0 mm -250M 250M
500.0 mm -500M 500M
600.0 mm -600M 600M
2.000 in -0200 0200
4.000 in -0400 0400
6.000 in -0600 0600
8.000 in -0800 0800
10.000 in -1000 1000
20.000 in -2000 2000
24.000 in -2400 2400

Measuring Range i

extension #
+25 mm -025M 025M
+50 mm -050M 050M
+100 mm -100M¹ 100M
+1.00 in -100T 100T
+2.00 in -200T 200T
+4.00 in -400T¹ 400T

Temperature Range

degrees #
-40 °C to 100 °C (-40 °F to 210 °F) -ST ST
-40 °C to 150 °C (-40 °F to 300 °F) -HT1 HT1

Model Number:  3543_ _ _ __ _ _ __ _

Model Number:

3543_ _ _ __ _ _ __ _

Model 3543 Available Versions: Any combination of gauge length, measuring range and temperature range listed above is available, except as noted. Intermediate and longer gauge lengths are easily attained by adding gauge length spacers.

¹Not available in 50 mm or 2 inch gauge length models.

Example: 3543-0800-400T-ST: 8.0 inch gauge length, +4 inch measuring range, standard temperature range (-40 °F to 210 °F)


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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