What Are the Differences Between Magnetic Scales and Optical Gratings for Linear Motors?

Linear motors are high-performance linear actuators used in industrial automation, machine tools, and semiconductor manufacturing due to high precision, speed, and acceleration. Position detection for linear motors commonly uses optical gratings and magnetic scales.

1. Principles of gratings and magnetic scales

Optical gratings use optical interference for high-precision position measurement. They consist of a glass or plastic substrate and alternating transparent and opaque regions that form interference fringes. Movement changes fringe position and allows displacement calculation. Optical gratings provide very high precision and resolution.

Magnetic scales use magnetic principles for position detection. A magnetic tape and read head produce voltage changes as the head passes magnetic patterns; measuring these signals yields displacement. Magnetic scales are robust against interference, operate across wide temperature ranges, and suit harsh environments.

2. Performance comparison

2.1 Accuracy and resolution: Optical gratings generally outperform magnetic scales, offering sub-micron precision and higher resolution. Magnetic scales are limited by magnetic material properties and head sensitivity, typically delivering micrometer-level accuracy.

2.2 Response speed: Optical gratings can reach tens of kHz, while magnetic scales typically reach hundreds of kHz, depending on design.

2.3 Environmental adaptability: Magnetic scales resist light and electromagnetic interference and tolerate dust and pollution, making them suitable for harsh environments. Optical gratings require cleaner environments and stable illumination.

3. Summary

Choose optical gratings where the highest precision and resolution are required and environmental conditions are clean. Choose magnetic scales for robust performance in harsh or contaminated environments. Combining both technologies can leverage their strengths to improve motion control precision and stability.