Precise Measurement of Strain: An extensometer directly measures the elongation or deformation of the specimen during the test. It provides accurate and reliable data on the strain, allowing for precise calculation of material properties such as modulus of elasticity, yield strength, and elongation. This direct measurement reduces the potential errors and uncertainties associated with indirect strain measurements or calculations based on displacement.

Improved Accuracy and Resolution: An extensometer typically offers high accuracy and resolution in measuring strain. It can capture small changes in the specimen's length, enabling precise determination of strain values, especially at low levels. This level of accuracy is particularly important when evaluating materials with low elongation or measuring the elastic modulus in the initial linear region of the stress-strain curve.

Enhanced Repeatability and Reproducibility: The use of an extensometer improves the repeatability and reproducibility of tensile test results. By directly measuring strain, it minimizes variability introduced by manual or visual strain measurements, which can be subjective and prone to human error. This enhances the consistency and reliability of test data, allowing for more accurate comparisons between specimens, materials, or testing conditions.

Compliance with Testing Standards: Many testing standards and specifications require the use of an extensometer to accurately measure strain during tensile testing machine. By using an extensometer, manufacturers can ensure compliance with industry standards and regulatory requirements. This ensures consistency and enables meaningful comparisons of test results across different laboratories or testing facilities.

Evaluation of Nonlinear Behavior: In addition to measuring strain in the linear elastic region, an extensometer can capture the non-linear behavior of materials, such as strain hardening or strain softening. This allows for a comprehensive characterization of the material's mechanical response and aids in understanding its deformation characteristics under varying loads.

Increased Testing Efficiency: The use of an extensometer streamlines the testing process by providing real-time, continuous measurements of strain. This eliminates the need for manual strain measurements at specific intervals or stopping the test to evaluate strain manually. The continuous data acquisition enables faster testing and improves overall testing efficiency.

Overall, the inclusion of an extensometer in tensile testing enhances the accuracy, repeatability, and reproducibility of the results. It provides precise strain measurements, improves compliance with testing standards, and enables a comprehensive evaluation of material behavior, ultimately facilitating better material selection, quality control, and design decisions.