A new system for direct measurement of yarn mass with 1mm accuracy

In textile production, measurement of the yarn mass in 1 mm range is utmost importance to properly evaluate the evenness, as several irregularities occur in 1 to 4 mm yarn length. Until present, measurements in 1mm range are still not directly performed. In this paper we present a direct mass measurement in 1 mm range based on capacitive sensors and signal processing techniques. The results point out that the evaluation of yarn mass, with this approach, is feasible in the 1 mm range. The new approach allows online measurement (1 mm yarn mass) in a spinning frame for real-time control. Several digital signal processing techniques are used to improve the results. A value of capacity variation is close to 2.08E-17 F for a 57 tex (0.057 g/m) yarn. It is possible, with this equipment, to detect small variations but signal to noise ratio (SNR) is still low. With the current electronic conditioning it is possible to detect these variations in spite it is in microvolt range. As a spin-off the developed sensor is being used in knitting machines to control the yarn break and bobbin end.