Extensometers
An extensometer is a strain measurement device used to measure the extension of a specimen under load. Extension measurement is one of ZwickRoell’s core competencies.
Contact extensometers Optical extensometers Selection criteria
What is an extensometer?
An extensometer is a strain measurement device used to measure the extension of a material under load.
- The extension of a material is a physical deformation that occurs when it is subjected to a load such as the pulling force associated with tensile testing. In addition to strain caused by tensile loads, extensometers also help determine compressive deformation or deflection under different types of load applications, including cyclic tests (incl. fatigue tests), compression tests and flexure tests.
- Extensometers measure strain directly on the specimen. This eliminates measurement influences from other testing components and increases accuracy.
- Strain measurement is required in the determination of characteristic values of a material. The tensile modulus, Young's modulus, yield point, strain at break, r-value and Poisson’s ratio are typical values determined with an extensometer. This information is essential when comparing materials, and help manufacturers determine whether they are able to withstand the loads to which they are subjected when used for their intended purpose.
- Extensometers are used in a wide variety of industries and an even wider range of materials. Examples include metals, plastics, fiber-reinforced composites, elastomers, films, textiles, ropes, paper and wood.
Optical / non-contact extensometers
Optical extensometers (video extensometers and laser extensometers) measure without contact and therefore have no influence on the determination of the characteristic values of a material. An additional advantage provided by strain measurement devices featuring non-contact measurement is that they can be used right up to break without risk of damage, even with specimens that are critical in this respect.
More information on our video extensometers and laser extensometers can be found under the following links:
Optical extensometers (video extensometers and laser extensometers) measure without contact and therefore have no influence on the determination of the characteristic values of a material. An additional advantage provided by strain measurement devices featuring non-contact measurement is that they can be used right up to break without risk of damage, even with specimens that are critical in this respect.
More information on our video extensometers and laser extensometers can be found under the following links:
Why choose an extensometer from ZwickRoell?
ZwickRoell extensometers are:
- One of our core competencies resulting from decades of application technology experience.
- Developed and manufactured in-house alongside our other testing components, guaranteeing full testing system compatibility.
- Designed to exceed standard requirements, since extensometer accuracy is essential for reproducible and reliable test results.
Selection criteria
Almost all tensile testing standards such as ASTM and ISO require strain measurement. The best suited extensometer for an application depends on the requirements set forth by the standard as well as the material properties of the specimen.
Determination of the ideal extensometer is based on six main criteria. These include properties that must be met, such as extensometer accuracy, resolution, measurement range, required measured values and the test temperature at which the extensometer will be used. But the key added value is provided by features such as easy handling, reduced learning curve, the scope of functionality, cost per test and further information provided by added options.