Laser Tracker Volumetric Error Mapping Mechanics during Precision Tool Transfer
Precision tool transfer requires distributed atmospheric compensation and multi-station laser tracker network bundling to prevent structural drift errors.
Edlen Atmospheric Equation
Meaning
Empirical formulas calculate the refractive index of air to adjust optical distance measurements for atmospheric effects. The edlen atmospheric equation uses environmental data to predict how much a laser beam will slow down in a factory setting. This correction is required for any long-distance measurement using a laser tracker or interferometer.
Without this adjustment, the reported distances would be inaccurate by several parts per million.
Variable Input
Inputs for the calculation include the air temperature and pressure alongside humidity levels. Sensors mounted on the measurement instrument provide these values in real time to the control software. Any error in these readings directly degrades the accuracy of the distance calculation.
Correction Mechanism
Correcting for the refractive index involves dividing the measured phase shift by the calculated index of the medium. This process restores the light’s travel time to its vacuum equivalent for distance derivation. The edlen atmospheric equation is the industry standard for performing this task in air-based metrology.
Application Boundary
The validity of the result depends on the air being relatively clean and free of heavy contaminants. Extreme conditions such as very high humidity or high altitudes require modified versions of the formula. This equation remains accurate for most indoor industrial environments where the temperature is controlled.