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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.

Gauge Lengths:

70 – 100 mm

Measuring Ranges:

±0.5 mm

Temperature Range:

-265 °C to 200 °C with -LHT option

Key Features:


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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 gage 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 (0.020 inches). Gage points are included with the extensometers and optional gluing fixtures are 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. 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.
  • Model 3909 for simple performance testing per NCHRP Report 465, and determining dynamic modulus of hot mix asphalt per AASHTO TP062.
  • 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 high quality foam lined case.
  • Rugged, dual flexure design for improved performance.
  • Easy mounting, attaches with magnets, which allows dynamic testing to 40 Hz.


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


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


≤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)


Integral, ultra-flexible Teflon® cable, 2.5 m (8 ft) standard

Operating Force:

<30 g typical
  • Gauge length adapters
  • Gluing fixture for gage points
  • Connectors to interface to nearly any brand test equipment
  • Shunt Calibration
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