What device is used to measure the strain during a test?

The device used to measure strain during a test is an extensometer. An extensometer is specifically designed to monitor the elongation or deformation of a material by measuring the distance between two points on the specimen as it is subjected to stress. This allows for precise calculations of strain, which is defined as the ratio of the change in length to the original length of the material.

In the context of material testing, such as tensile tests, accurate measurement of strain is crucial to determine the material's properties, including its elasticity, strength, and ductility. Extensometers can be mechanical or electronic, and they provide detailed data that can be used to plot stress-strain curves, essential for analyzing a material’s performance under various load conditions.

While other devices like calipers or gauges might serve measuring functions, they do not specifically measure strain in the same way an extensometer does. A manometer is used for measuring pressure, making it unrelated to strain measurements. Thus, the extensometer is the most appropriate choice for measuring strain during tests.