Extensometers for Simple Performance Testing of Asphalt – Model 3909

Designed for measuring axial displacements in the simple performance tests prescribed by NCHRP Report 465, and determining dynamic modulus of hot mix asphalt per AASHTO TP062.

Epsilon extensometers are COMPATIBLE WITH VIRTUALLY EVERY BRAND OF TEST EQUIPMENT and can be supplied with the correct connector to plug in directly, or supplied with a separate conditioner and amplifier.

WITH EPSILON’S 20+ YEAR HISTORY OF SERVICE to the materials testing community, you know we will be there to stand behind our products when your critical application requires it.

36 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.

These extensometers are typically mounted as two axial modules with independent outputs capable of measuring specimen deformations in two locations, but they can be mounted as a single unit or up to four on a sample. They quickly clip onto gauge points mounted per the test requirements.

Magnets at each end of the extensometer snap instantly in place on the steel gauge points glued to the test sample. The quick attachment is most advantageous when testing preconditioned samples that are heated or cooled, since the extensometers can be mounted before the sample changes temperature appreciably. For units intended to be used inside triaxial cells, extensometers are available with modules rotated 90°.

The standard Model 3909 has full scale measuring range of ±0.5 mm or ±0.020 inches. Gauge points are included with the extensometers and an optional gluing fixture is available. Two standard 3909 units can be converted to the Model 3910 with the purchase of optional gauge length adapters.

The Model 3909 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 with electronics for a strain channel, and Epsilon will equip the extensometer with a compatible connector that is wired to plug directly into the controller. For systems lacking the required electronics, Epsilon can provide a variety of signal conditioning solutions that enable connecting to data acquisition systems or other equipment.

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  • Model 3909 for simple performance testing per NCHRP Report 465, and determining dynamic modulus of hot mix asphalt per AASHTO TP062.
  • Easy mounting, attaches with magnets, which allows dynamic testing to 40 Hz.
  • Full bridge, 350 ohm strain gaged design for compatibility with nearly any test system.
  • All standard units have linearity readings of 0.20% or better.
  • Includes the Epsilon Shunt Calibration System for on-site electrical calibration.
  • Rugged, dual flexure design for improved performance.
  • Includes high quality foam lined case.

Download Data Sheet


Measuring Range: ±0.5 mm or ±0.020 inches

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

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

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 Teflon® cable, 2.5 m (8 ft) standard

Operating Force: <30 g typical



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  • Adjustable fixture for gluing gauge points to test samples (recommended) – adjustable for offset height and gauge length; configurable for various specimen diameters and mounting gauge points at 90°, 120°, and 180°
  • Gauge length adapters
  • 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 #
70.0 mm -070M¹ 070M
76.0 mm -076M 076M
100.0 mm -100M 100M
2.750 in -0275¹ 0275
3.000 in -0300 0300
4.000 in -0400 0400
Model Number:  3909 – _ _ _
Model Number:
3909 – _ _ _

Model 3909 Available Versions: Available in intermediate and larger gauge lengths on special order. Other configurations may be available with special order; please contact Epsilon to discuss your requirements.

±0.5 mm measuring range will be supplied with units that are ordered with gauge lengths in mm units.
±0.020″ measuring range will be supplied with units that are ordered with gauge lengths in inch units.
¹Special order.

Example: 3909-0300: 3.000 inch gauge length with a full scale measuring range of ±0.020 inches


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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