Magnetic sensors

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 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.
 

Active magnetic sensor or passive magnetic sensor?

Apart from differentiating between incremental and absolute magnetic field sensors, another factor to be considered is whether the sensor is active or passive. Passive MagLine sensors supply a signal that cannot be processed externally, and for this reason must be connected to a downstream electronic system such as a MagLine measurement display or a MagLine electronic evaluation system. An active SIKO magnetic sensor already converts the received signal and has a standardized interface through which it can forward the information to a higher-level control, i.e. a downstream electronic unit. The MS sensors of the MagLine series have passive properties, while the MSK sensors run actively towards the exterior.
 

Magnetic length measurement and magnetic angle measurement in many fields

Magnetic sensors can be used in a wide range of fields, especially in environments in which the components can be exposed to dirt and loads and if the absolute accuracy is not mandatory. These applications include:
 

• Linear encoders for dowel drilling stations, parquet floor production, tubular film packaging (MagLine Micro)
• CT patient tables, mirror tracking (solar power stations), format circular saws, stone cutting (MagLine Basic)
• Stage equipment, forklift trucks, waste and scrap metal presses, cutting stone (MagLine Macro)
• Wind power generators, elevators, pipe bending systems, access control systems (MagLine Roto) 

The overview of the product ranges shows which applications require which type of magnetic measuring equipment. Within the product families all components from the sensor to the magnetic strip and the display are ideally combined.
Note: Magnetic sensors are part of the MagLine product range.

Note: Magnetic sensors are part of the MagLine product range.