Magnetic sensors

Incremental and absolute MagLine magnetic sensors

Information gathered on magnetic tapes or magnetic rings is translated by sensors and transferred to translation modules. Values measured by active sensors are converted into digital counting pulses, analog sine-cosine signals or serial absolute values. For passive sensors, combination with displays or translation modules is required.

Magnetic sensors as an inexpensive alternative to optical sensors

Magnetic sensors are hallmarked by robustness and cost efficiency. With their non-contacting design they are non-wearing and insensitive to soiling in comparison to optical sensors, for example. Magnetic sensors therefore only require little or no servicing. In addition they are more flexible during installation: The distances between the magnetic sensor and strip can be considerably larger than with an optical measuring system. The following versions are available:

• Various sizes through to a board solution
• Individual connector options
• Installation in customized housing

Incremental and absolute measuring technology

When selecting a suitable sensor the first question always concerns the measuring method – incremental or absolute? Incremental measurement is popular and as a general rule also less expensive: A magnetic strip is encoded with regularly arranged north and south poles; the pole length also determines the maximum resolution and system accuracy. A sensor head which accommodates the sensor elements moves over the encoder at a defined distance and reads the magnetic fields that are processed as square wave signals (counting pulses). The distance traveled is indicated by the number of pulses.

The magnetic absolute measurement is carried out by a dual-track strip, i.e. on one side there is an incremental track, while the other track features absolute encoding. This encoding therefore only occurs once over a specific length. The advantage is that the sensor always knows its exact current position – also in a non-energized state. In contrast, in the event of a power failure the incremental method requires a reference operation to take the sensor back to a certain reference point that is then signaled back to the control unit. To avoid this process step, SIKO supplies so-called quasi-absolute sensor solutions. The necessary measuring data are stored by means of a battery. Referencing is therefore also no longer necessary with these systems, for example after power failures. In many medical and analysis fields this preventative measure is an essential safety feature. This problem can, however, be fully avoided with the real absolute sensor technology.

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