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). These units were designed to fit inside small inner diameter vessels.

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

A PDF document containing specifications on the 3544 can be downloaded from the following link: PDF DOWNLOAD.

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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.
• Rugged, dual flexure design for strength and improved performance.
• Includes high quality foam lined case.
• 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.

Options:

Horizontal, vertical, or user convertible orientations

Connectors to interface to nearly any brand test equipment
Shunt Calibration Module

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