Which Is More Accurate: Optical Grating Scale or Magnetic Grating Scale?

In precision measurement, optical grating scales and magnetic grating scales are common displacement sensors whose accuracy is critical. Which is more accurate depends on many factors.

Effect of working principle on accuracy

Optical grating scale: based on optical interference and diffraction

Optical grating scales use interference/diffraction and consist of a grating scale and a read head. The grating has alternating transparent/opaque lines producing Moiré fringes when illuminated; movement of these fringes corresponds to displacement. Optical methods can reach sub-micron or even 0.01 μm resolution, making them ideal for semiconductor and optical instrument manufacturing.

Magnetic grating scale: based on magnetic-to-electric conversion

Magnetic grating scales record periodic magnetic signals on a magnetic strip and use a read head to sense changes. Typical magnetic scale resolution is around 0.1 μm, which limits its use in extremely high-precision scenarios.

Accuracy comparison

Optical scales generally offer higher resolution and accuracy (e.g., ±1μm~±3μm for high-end products), while magnetic scales provide robust performance in harsh industrial environments with typical accuracies around ±0.01mm or ±10μm/m.

Environmental robustness

Optical scales are sensitive to dust, oil and temperature, requiring clean, temperature-controlled environments for best accuracy. Magnetic scales are more tolerant to contamination and harsher conditions, and with proper shielding can remain stable under typical industrial EMI.

Cost considerations

High-precision optical scales are more expensive due to demanding manufacturing and materials; magnetic scales are more cost-effective for moderate-precision applications.

Conclusion

Optical grating scales can achieve higher accuracy under controlled conditions, while magnetic grating scales excel in industrial robustness and cost-effectiveness. Choose based on application needs: precision and clean environment favor optical scales; harsh environments and cost sensitivity favor magnetic scales.