Whether performing routine tensile testing, measuring Poisson’s ratio, or conducting full-field strain analysis, correct sample marking is essential for reliable, repeatable strain data. This article provides a comprehensive guide to sample marking for video extensometers, explains how digital image correlation (DIC) works, and outlines best practices for achieving high-quality strain measurements across a wide range of materials.

If you’re trying to choose between a video (non-contact) extensometer and a clip-on (contact) extensometer, the best answer depends on what you test, how often you change specimen types, your accuracy needs, your risk tolerance for damaging samples, and—very often—budget.

A clip-on extensometer is a mechanical strain measurement device that attaches directly to the specimen during a tensile or compression test.