Comparison between capacitive and photoelectric yarn measuring heads

Abstract:

Electronic yarn Clearers ensures excellent clearing to be obtained with minimum mechanical stress on the yarn. The places which are not possible to clear with the mechanical system are an additional feature of the electronic clearing system. One panel central adjustment for several spindles leads to a significant saving of time.

Comparison:

Currently two types of electronic yarn clearers are available; capacitive and photoelectric. Comparison of these two is as follow:

Properties	Capacitive type EYC	Photoelectric type EYC
Detection method	Two parallel plate capacitor is used in which air and material of yarn is used as dielectric medium.	Yarn is passed between a light source and a photoelectric cell.
How it works?	The variation in capacitance is proportional to the mass of the short length of moving yarn between the plates of the capacitor.	Amount of light received by the photocell determine the yarn thickness.
Fault limits	Thick (long & short) thin (long &short) places and neps are detected.	Only thick (long & short) and thin (long &short) places were detected.
Phenomena	Detection phenomena is as:	Detection phenomena is as:
Evaluation	The fault is evaluated with the full increase of the cross-section in percent.	The fault is evaluated with the full increase of the diameter in percent.
Variations detection	Yarn mass variations are detected by the capacitive measuring device.	Yarn diameter variations are detected by the optical measuring.
Accuracy & Sensitivity	The capacitive measurement principle has a high measurement accuracy and a sensitivity that is stable over many years.	The optical measurement principle is less sensitive to diameter changes and less stable over a long time than the capacitive.
Suitability	The capacitive measurement principle is unsuitable for environments with strong air-humidity changes or for electrically conductive yarns.	The photoelectric measurement principle is suitable for humid environments and could be used for electrically conductive yarns.
Voluminous fault detection	Visually large appearing yarn fault is considered as in-significant because the number of additional fibers are not extremely high.	Visually large appearing yarn fault is considered as significant because the number of additional fibers absorb more light.
Contamination detection	The change of the yarn signal caused by the contamination is compensated within certain limits. If the contamination gets too high, a technical alarm is triggered.	Contamination is clearly detected and signal is sent to amplifier to activate cutter to cut the fault.
Humidity effects	Non-homogenous yarn humidity can lead to unjustified cuts.	Very dry yarns exhibit a higher hairiness. This suggests a larger diameter and can lead to unjustified cuts.
Pros	Advantages: v  Purity of material can be detected v  More sensitive	Advantages: v  Change in color can be detected v  Change in cross-section can be detected v  Moisture will not affect the result
Cons	Drawbacks: v  Change in color cannot be detected v  Moisture in and outside the material will change the dielectric value hence result will fake.	Drawbacks: v  Excess of moisture can damage camera (photocell) v  Purity of material cannot be detected v  Change in depth cannot be detected v  Change in dimension cannot be detected v  More maintenance and clearing is required v  Less sensitive

Conclusion:

After all above discussion and comparison, I concluded that both capacitive and photoelectric yarn clearers are perfect in their own limits but there is always a possibility to declare one as best than other. I will say capacitive yarn clearer is best for Pakistani industries, if moisture management is good. It could be clearly seen in above comparison that photoelectric has more drawbacks as compare to capacitive, one major of them is that it needs more maintenance. Measuring device should be adopted according to requirement such as color detection is not possible with capacitive but it is possible with photoelectric.

So, according to advantages and drawbacks capacitive is best but device should be used according to most prior requirements for better results.

References:

v  Textile In Depth (http://www.textilesindepth.com/yarn-faults-clearing/)

v  Textile Fashion Study (http://textilefashionstudy.com/yarn-cleaner-types-of-yarn-cleaner-use-of-yarn-cleaner/)

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