Few words about Microtex sensors for textile applications
The Microtex sensors developed up till now for textile applications are mainly devoted to weft detection in air-jet looms.
A basic distinction must be done about the physical detection principle:
Microtex sensors are based on transmitted light, and not on reflected light.
With transmitted light sensors, the yarn detection signal is due to the quantity of light subtracted by the yarn from a fixed uniform optical field, produced by the sensor in the reed channel.
Two main features come down from this principle:
- High reliability: the detection signal is not dependent on the light reflected by the yarn, in particular on its colour, and is not dependent on the position of the yarn in the sensor optical field, that is on the yarn position in the reed channel,
- High sensitivity: a careful control of the geometrical and optical field design parameters allows the detection of the thinnest yarns.
For the above reasons the transmitted light principle must also be adopted in the devices dedicated to the control and the measurement of the yarn titre.
In general, two main criteria are adopted in the weaving technique for the weft detection for what concerns the position of the sensor along the reed:
- the sensor is positioned at any wanted intermediate point of the reed, to allow the production of different height fabrics from a single reed,
- the sensor is positioned at the end of the reed on a reed extensor device, so that reeds of different lengths are necessary to produce fabrics of different heights.
Microtex produces sensors for each and for both these applications, as described in detail in the following.
In particular, as the sensors based on transmitted light, for the above application 1), are, in general, mechanically invasive of the space between two adjacent reed dents, causing possible draw-backs in the weaving process, Microtex recently developed a sensor - MTX-NT01 - which is not invasive and, thanks to a return optical weft control, adds a four-times incremental sensitivity to the high reliability of the sensors based on transmitted light.
