The yarn length measuring instrument is a key device used in the textile industry to accurately measure the length of yarn. It is widely used in yarn production, quality inspection and research and development. The following is its standard operating procedures and precautions:

I. Preparation

1. Equipment inspection

(1) Confirm that the instrument is placed horizontally to avoid vibration or tilt affecting the accuracy.

(2) Check whether the yarn guide wheel, tension device, counter and other components are clean and free of wear.

(3) Calibrate the instrument (refer to the manufacturer's manual) to ensure that the measurement error is within the allowable range (usually ≤±0.5%).

2. Environmental requirements

Temperature: 20±2℃, humidity: 65±5% (avoid moisture absorption or drying of the yarn causing length changes).

3. Yarn sample

The sampling must comply with the standard (such as GB/T 4743), remove the surface hairiness or knots, and avoid affecting the tension.

II. Operation steps

1. Sample loading

(1) Fix the yarn tube on the unwinding frame, and lead the yarn through the yarn guide hook and tensioner in turn (set the tension according to the yarn type, such as 0.5±0.1cN/tex for cotton yarn).

(2) Make sure that the yarn is not entangled or twisted, and the end is fixed on the clamp of the winding arm.

2. Parameter setting

Preset length: Enter the target measurement length (such as 100 meters). Some instruments need to set the number of winding turns (circumference × number of turns = target length).

Speed adjustment: Select a low speed (such as 30m/min) to reduce tension fluctuations. High-count yarn or fragile yarn needs to be further reduced.

3. Start the measurement

(1) Press the start button, the instrument will automatically wind the yarn and count.

(2) Observe whether the yarn tension is stable. If the yarn breaks or slips, pause and adjust immediately.

4. Data recording

After reaching the set length, the instrument automatically stops and records the actual length on the display (such as 100.2 meters).

Repeat the measurement 3-5 times to get the average value to improve accuracy.

5. End the operation

Cut the yarn, remove the sample, and clean the residual fiber in the instrument.

III. Notes

1. Tension control

Too much tension will cause the yarn to stretch, and too little tension will cause the yarn to be loose. It needs to be adjusted according to the yarn material (such as chemical fiber/natural fiber).

2. Abnormal handling

(1) If the length deviation is greater than 1%, check the calibration of the tensioner or whether the yarn is slipping.

(2) Regularly verify the accuracy of the instrument with a standard yarn sample (e.g. calibrate after every 50 measurements).

3. Maintenance

Clean the yarn guide parts daily, lubricate the moving joints monthly, and have a comprehensive inspection by professionals every year.

IV. Application examples

Quality control: Measure the difference between the actual length of the yarn and the nominal length, and calculate the weight deviation per 100 meters.

Process adjustment: Evaluate the winding uniformity of the winder through multiple measurements.

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