Miniature Averaging Axial Extensometers – Model 3442RA1

With gauge lengths of 25 and 50 mm (1 and 2 inches) and measuring ranges of 1.2 and 2.5 mm (0.050 and 0.100 inches), the Model 3442RA1 was designed for applications where tensile or compressive strength tests on small rock, concrete and other small compression samples is desired.

Model 3442RA1

38 EXTENSOMETER MODELS are available in many thousands of variations. Our focus on helping customers has led to the development of models to cover nearly any test method.

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


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


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

Axial strain is measured on opposite sides of the test specimen and the output is an average of the two readings. The Model 3442RA1 is available in a variety of configurations for samples 50 mm (2 inches) or smaller in diameter. All are self-supporting on the specimen and mount very easily. The conical point contacts included with the extensometer are made from tungsten carbide. If desired, the two cut-outs can be independently configured, providing two readings. Epsilon has versions for use in oil to 1360 bar at 200 °C (20,000 psi at 400 °F). These units will fit in small inside diameter vessels. For large diameter specimens, we suggest one of the Model 3542RA averaging axial extensometers.

The Model 3442RA1 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


  • Full bridge, 350 ohm strain gaged design for compatibility with nearly any test system.
  • High accuracy, averaging output or optional dual independent outputs.
  • Designed for smaller diameter specimens.
  • Easy mounting, attaches with integral springs.
  • Self-supporting on the specimen.
  • Includes the Epsilon Shunt Calibration System for on-site electrical calibration.
  • Rugged, dual flexure design for strength and improved performance.
  • 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

Accuracy: Standard configurations meet ASTM E83 class B-1 and ISO 9513 class 0,5 requirements for accuracy. A test certificate is included.

Linearity: ≤0.20% of full scale measuring range, depending on model

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

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

Operating Force: <30 g typical per side



Download Data Sheet

  • Dual, independent outputs
  • Connectors to interface to nearly any brand of test equipment

Download Data Sheet


Ordering Information

Click table options to configure

Gauge Length i

mm or inches #
25.0 mm -025M 025M
50.0 mm -050M 050M
1.000 in -0100 0100
2.000 in -0200 0200

Measuring Range i

extension #
±1.25 mm -125M 125M
±2.50 mm -250M 250M
±0.050 in -050T 050T
±0.100 in -100T 100T

Temperature Range

degrees #
-270 °C to 100 °C (-454 °F to 210 °F) -LT LT
-40 °C to 100 °C (-40 °F to 210 °F) -ST ST
-40 °C to 150 °C (-40 °F to 300 °F) -HT1 HT1
-40 °C to 200 °C (-40 °F to 400 °F) -HT2 HT2
-270 °C to 200 °C (-454 °F to 400 °F) -LHT LHT

Model Number:  3442RA1_ _ _ __ _ _ __ _

Selected Compressive Measuring Range: _ _ _ _

Model 3442RA1 Available Versions: ANY combination of gauge length, measuring range and temperature range listed above is available, except as noted. Test specimen diameter(s) must be specified at the time of order. Other configurations may be available with special order; please contact Epsilon to discuss your requirements.

Example: 3442RA1-0200-050T-ST: 2.0 inch gauge length, 0.050 inch measuring range, standard temperature option (-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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