VIT 320 – Photoelectric Fiber Length Tester

Testing Method

What is Fiber Length?:

Fiber length is the distance between the two ends of a fiber when fully straightened without external force. It is measured in millimeters (mm). Fiber length is crucial for determining spinning equipment settings, process parameters, and yarn quality, making it a key indicator of fiber quality. While chemical fiber length can be controlled artificially, natural fiber length forms naturally, making its measurement particularly important.

Fiber Length Index For cotton fiber, length is not uniform. Key indexes used to express cotton fiber length and distribution include:

• Modal Length: The most common fiber length in a sample.
• Quartile Length: The average length of fibers longer than the modal length, crucial for setting roller gauge parameters in spinning.
• Short Fiber Content: The percentage of fibers shorter than a specified length limit. When this exceeds 15%, yarn strength and evenness deteriorate significantly.

Test Principle:

The tester uses optoelectronic technology to measure fiber length. A sample of about 120g of loose cotton fibers is randomly selected, secured with a spiral comb clip, and straightened under controlled tension. The fibers pass through the optoelectronic instrument, where a signal light source irradiates them. The photoelectric receiver detects light intensity variations, generating a fiber length distribution curve and calculating various fiber length indexes.

Methods of Measuring Fiber Length There are three primary fiber length measurement methods:

• Grouping Weighing Instruments: Clear in principle but complex to operate, with multiple uncontrollable error sources.
• Automatic Instruments: Require samples to be stored in a humidity-controlled environment before testing, as static electricity can affect results.
• Photoelectric Fiber Length Testers: Highly accurate and efficient, offering more indexes than traditional methods, fast testing speed, and good result repeatability. They provide upper half average length, length uniformity ratio, and short fiber content index, making them easy to operate and highly reliable.