Circumferential Extensometers – Model 3544

Designed for concrete and rock compression testing or for compression tests on other large samples. This model may be used simultaneously with the Model 3542RA axial extensometers.

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.

Circumferential extensometers measure the change in circumference as the sample is compressed. This is considered by many researchers to be a more accurate way to determine diametral strain, since the measurement is taken over the entire material inside the circumference.

A high precision, custom roller chain with special rollers mounts the extensometer to the specimen. As the specimen diameter enlarges during the test, the chain causes the extensometer to expand. The unit is self-supported on the sample with integral springs. Links are easily added or removed to adjust for different size specimens. A mechanical adjustment allows the output to be set to zero. A breakaway device protects the extensometer in the event of specimen rupture. Often rock specimens are tested in tri-axial pressure cells. Versions of the Model 3544 are available to fit inside the vessel and operate in oil environments at up to 1360 bar at 200 °C (20,000 psi at 400 °F).

The Model 3544 is the best choice for large diametral strains in large compression samples. Epsilon’s diametral rock and concrete extensometer, Model 3975, is recommended for small strain measurements such as Poisson’s ratio.

The Model 3544 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.

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  • Full bridge, 350 ohm strain gaged design for compatibility with nearly any test system.
  • Adapts to a wide range of specimen sizes by adding or removing chain links.
  • Self-supporting on the specimen.
  • May be used simultaneously with Model 3542RA axial extensometers.
  • Versions available for use in tri-axial confining pressure cells, at high pressures and temperatures.
  • 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

Linearity: ≤0.25% of full scale measuring range

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 Sizes: Fits round specimens with diameters from 50 mm up to 200 mm (2-8 inches), depending on configuration



Download Data Sheet

  • Horizontal, vertical, or user convertible orientations
  • Connectors to interface to nearly any brand of test equipment

Download Data Sheet

Product Videos


Setup instructions for Model 3544 circumferential extensometers.


Ordering Information

Click table options to configure

Diameter Range

mm or inches #
50 mm to 100 mm -100M 100M
50 mm to 150 mm -150M 150M
50 mm to 200 mm -200M 200M
2.00 in to 4.00 in -0400 0400
2.00 in to 6.00 in -0600 0600
2.00 in to 8.00 in -0800 0800

Circumferential Measuring Range

extension #
+2.0 mm -020M 020M
+3.0 mm -030M 030M
+6.0 mm -060M 060M
+12.0 mm -120M 120M
+0.080 in -080T 080T
+0.125 in -125T 125T
+0.250 in -250T 250T
+0.500 in -500T 500T

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
-40 °C to 200 °C (-40 °F to 400 °F) -HT2 HT2

Model Number:  3544 – _ _ _ __ _ __ _

Model Number:

3544 – _ _ _ __ _ __ _

Model 3544 Available Versions: Any combination of diameter range, measuring range and temperature range is available, except as noted. Other configurations may be available with special order; please contact Epsilon to discuss your requirements.

Example: 3544-200M-120M-ST: 50 mm to 200 mm diameter range, +12 mm measuring range, standard temperature option (-40 °C to 100 °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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