Differences Between Optical Grating Scales and Magnetic Grating Rulers in Linear Motor Modules

With the arrival of Industry 4.0, traditional production is gradually replaced by automation, and linear motion products are booming. A linear module consists of a mover, stator, encoder, scale, cables, etc. Today Atonm shares the differences between optical grating scales and magnetic grating rulers in linear motor modules.

Magnetic grating rulers use a recording method similar to tape recording: a recording head writes strictly periodic magnetic waves on the magnetic tape (or disk). The recorded magnetic waveforms form the magnetic grating. The distance between adjacent grating waves is called the grating wavelength or pitch.

Atonms magnetic grating displacement sensors share ABZ phase pulse outputs with optical grating displacement sensors and can interface with similar display and acquisition systems. However, magnetic grating displacement sensors are commonly used where optical gratings are unsuitable. Optical grating displacement sensors are incremental encoders; after power loss they can retain positional data, while some incremental magnetic grating sensors may reset to zero. This is a primary difference between magnetic grating and optical grating displacement sensors.

Magnetic grating rulers are water-, oil- and dust-resistant, have strong vibration immunity and long service life. Their cost-performance advantage increases for lengths above 2 meters and they can reach ranges up to 40 meters. Atonms domestic magnetic grating rulers are competitively priced, robust and widely applicable.

Optical grating scales excel in precision and are cost-effective within 0–2 meters. Because of manufacturing constraints, producing optical gratings longer than 5 m is difficult. Optical scales use a semi-sealed design with some water, dust and swarf resistance, but exposure to oil, water, dust or heavy vibration can accelerate damage and shorten service life. Optical gratings are generally more expensive than magnetic rulers.

Above are the main differences between incremental magnetic grating rulers and absolute optical gratings in linear motor modules. Many customers seek alternatives to optical gratings to reduce cost; magnetic grating rulers can meet the requirements of some linear motors and provide a cost-effective, stable-performance replacement.