Keywords: Granite surface plate calibration, autocollimator, laser interferometer, uncertainty evaluation
Proper calibration and maintenance are critical to preserving plate accuracy:
- Calibration Methods:
- Autocollimators: Provide angular measurements with 0.05″ resolution.
- Laser Systems: Enable dynamic flatness profiling via interferometric analysis.
- CMMs: Use tactile probing for point-by-point verification.
A study comparing these methods found autocollimators fastest (5 min/plate) but CMMs most accurate (<0.3μm uncertainty).
- Maintenance Protocols:
- Cleaning: Use pH-neutral detergents to avoid chemical etching.
- Storage: Maintain ambient temperatures (20±2°C) and humidity (45-55% RH).
- Recalibration: Biannual checks are recommended; plates in high-use environments may require quarterly validation.
Uncertainty budgets, calculated using GUM principles, should include contributions from measurement equipment, environmental factors, and operator variability.
