What is the instrument used for yarn twist?

The instrument commonly used for measuring yarn twist is called a "yarn twist tester" or a "twist tester." It is a specialized device designed to accurately measure the twist in yarn samples. 

A yarn twist tester typically consists of the following components:

1. Clamps: These are used to securely hold the ends of the yarn sample during the testing process.

2. Rotating spindle: It is the central part of the instrument that rotates the yarn, allowing it to untwist.

3. Scale or counter: This component measures the number of rotations or twists as the yarn untwists.

4. Tensioning device: It helps provide the necessary tension to the yarn during the test to ensure accurate results.

The yarn twist tester allows for precise and consistent measurement of yarn twist, providing valuable information for quality control, yarn characterization, and meeting specific requirements in textile production.