Bi-Axial Averaging Extensometers –
Model 3560-BIA

A single integral unit provides simultaneous, averaged lateral (transverse) strain and averaged axial strain measurement for determining modulus and Poisson’s ratio.

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.


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

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


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

The model 3560-BIA is extensometer is ideally suited for routinely measuring modulus and Poisson’s ratio of advanced composites and other anisotropic materials. Transverse strain is averaged and provided as a single output. Axial strain is averaged and provided as a single output in the standard configuration. Model 3560-BIA is also available in an optional configuration that has separate outputs for the axial strain channels, which enables measurement of specimen bending with the testing machine’s software.

Standard configuration – two outputs (testing machine must have two strain channels):

  • Average axial strain (electrically averaged)
  • Average transverse strain (mechanically averaged)

Optional configuration – three outputs (testing machine must have three strain channels):

  • Left axial strain (for averaging using the testing machine’s software)
  • Right axial strain (for averaging using the testing machine’s software)
  • Average transverse strain (mechanically averaged)

The Model 3560-BIA uses a design unique to Epsilon, where the knife edges remain parallel during the displacement. This approach greatly reduces crosstalk between axes and allows use on round or flat specimens with equal ease. These extensometers are very easy to mount. Integral springs hold the unit on the test sample. The parallel multiple flexure design makes these units very durable.

The Model 3560-BIA 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 compatible connectors that are 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. The standard model 3560-BIA configuration requires two strain channels in the testing machine. The optional configuration requires three strain channels in the testing machine.

For customers who only need to measure modulus and do not need to measure Poisson’s ratio, Epsilon recommends the smaller, lighter, fatigue test rated model 3442AVG. 

Download Data Sheet

  • May be left on through failure with composites that fail progressively (non-explosive) and low-elongation materials.
  • Multiple sets of dual flexures and mechanical stops allow testing through failure and provide a rugged unit.
  • Full bridge, 350 ohm strain gaged design for compatibility with nearly any test system.
  • Includes the Epsilon Shunt Calibration System for on-site electrical calibration.
  • Rugged, dual flexure design for improved performance.
  • Knife edge mounting and parallel displacement allows mounting on round or flat specimens. Much easier to mount than designs using conical points (especially on thin flat specimens and round ones).
  • Self-supporting on the specimen.
  • High accuracy and minimal crosstalk between channels.
  • Includes high quality foam lined case and spare set of tool steel knife edges.

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 in the axial direction. A test certificate is included. All standard units have linearity of 0.15% full scale measuring range or better in the transverse direction.

Linearity: ≤0.15% 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

Specimen Size: Works with samples 2.5 to 25 mm (0.1 to 1 inch) width or up to 15 mm (0.6 inch) diameter

Operating Force: 30 to 50 g typical

Crosstalk: Less than 0.5%



Download Data Sheet

  • Connectors to interface to nearly any brand of test equipment
  • Two outputs or three outputs – specify when ordering
  • Adapters to fit larger specimens
  • Specialty Knife Edges

Download Data Sheet

Ordering Information

Click table options to configure

Gauge Length i
mm or inches #
10.0 mm -010M¹ 010M
25.0 mm -025M 025M
50.0 mm -050M² 050M
0.500 in -0050¹ 0050
1.000 in -0100 0100
2.000 in -0200² 0200
Measuring Range i
% strain (axial) / mm or inches (transverse) #  
±5% / ±1.0 mm or ±0.050 in -005³ 005
±10% / ±1.0 mm or ±0.050 in -010³ 010
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: 3560-BIA_ _ _ __ _ __ _

Model 3560-BIA Available Versions: ANY combination of gauge length, measuring range and temperature range listed above is available, except as noted. Other configurations may be available with special order; please contact Epsilon to discuss your requirements.

¹10 mm and 0.5 inch gauge lengths are only available in 10% axial measuring ranges.
²50 mm and 2.0 inch gauge lengths are only available in 5% axial measuring ranges.
³If the gauge length is ordered in mm units, then the transverse measuring range will be in mm. If the gauge length is ordered in inch units, then the transverse measuring range will be in inches.

Note: model 3560-AVG has been replaced by the smaller, fatigue test rated model 3442AVG.

Example: 3560-BIA-050M-010-HT2: 50.0 mm gauge length, ±10% axial strain measuring range/± 1.0 mm transverse measuring range, HT2 option (-40 °C to 200 °C)


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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Our 2022 Extensometer Catalog, Version 110 is now available! Not finding something you’re looking for? Ask us about a custom quote.