Magnetic length and angle measuring systems - SIKO - #8

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3.2 3.3 3.4 3.5 3.6 3.1 5.0 3.7 5 MagLine | 5.0 Product Overview www.siko.de MagLine – Magnetic length and angle measurement Technical Details A sensor registers the magnetically encoded path information and converts this to standardized interface signals for subsequent processing. Incremental to absolute measurement �¡�¡ incremental �¡�¡ quasi-absolute �¡�¡ true-absolute yes no no yes yes no Power interruption Sensor/band reading distance exceeded �¡�¡ A “quasi-absolute” measurement is achieved by buffering the measured data by means of a battery. Movement of the sensor along an incrementally encoded band is recognized even in a currentless state. Referencing is only necessary if the sensor exceeds the maximum band distance. �¡�¡ A “true-absolute” measurement is achieved when the magnetic strip is encoded absolutely, thus enabling all currentless movements of the sensor/ band to receive an absolute position signal direct from the magnetic band when the system is switched on. The system requires re-referencing if … + - Scanning method Band type + - The magnetic measurement principle The core element of magnetic linear measurement is a permanently mounted magnetic band (also called the scale). This band is scanned by a magnetic sensor which forwards the information either to an electronic evaluation system, a higher-level controller (PLC) or directly to a connected magnetic display. The actual magnetic linear measurement is based on the changes in resistance by magnetic effects. The magnetic bands used are encoded by SIKO in specially developed processes. These encoded scales are scanned by contactless sensors. The integrated electronic system converts the measured values into digital or analog signals for further processing, for example by controllers or a corresponding SIKO indicator. Incremental and absolute processes – the difference Magnetic linear measurement is performed either incrementally, quasi-absolutely or true-absolutely. Incremental method In incremental systems the magnetic band is magnetized at regular intervals with north and south poles, and the pole length also determines the maximum resolution and system accuracy. If the sensor is moved over the band, the periods generate the path information which is processed in the form of square-wave signals (counting pulses). Counting of the pulses provides information on the traveled path. In an incremental system at least one absolute reference is necessary – the so-called reference point. This point serves for re-orientation of the system and can be stored on the magnetic band as additional information. This reference point is also of importance due to the fact that the actual position value is generally lost in an incremental system if the power supply is interrupted (e.g., if the system is switched on and off) and if the sensor position has been changed in the meantime. A new referencing operation is then necessary. 8