ASTM G138 is the ASTM standard that covers calibration of a spectroradiometer using a standard source of irradiance. It is relevant for users who need dependable spectral measurements and a consistent calibration approach for optical testing or quality work. By defining a recognized calibration method, the standard helps support measurement accuracy, repeatability, and better comparison of results across instruments and testing environments.

Overview of ASTM G138

ASTM G138, Standard Test Method for Calibration of a Spectroradiometer Using a Standard Source of Irradiance, provides a technical framework for calibrating spectroradiometers against a known irradiance source. This is important when measurements must be traceable and aligned with controlled laboratory practice. The standard is generally used to support instrument setup, verification, and ongoing measurement confidence. For organizations that depend on spectral data, it offers a practical reference for consistent calibration procedures.

Common use cases of ASTM G138

This standard is commonly used in laboratories and testing environments where spectroradiometers are employed to measure radiant energy by wavelength. It may support calibration work for optical instruments used in performance testing, research, or product evaluation. ASTM G138 is also useful in workflows that require comparison of spectral data over time or between instruments, especially when a standard source of irradiance is used as the calibration reference.

Benefits of using ASTM G138

Using ASTM G138 can help improve measurement consistency and reduce uncertainty in spectroradiometer calibration. It supports quality control by giving teams a recognized test method for aligning instruments with a standard irradiance source. That can simplify procurement, internal procedures, and compliance review, while also helping reduce risk when spectral results are used for engineering decisions, verification tasks, or product assessment. For organizations managing optical measurements, it adds structure and reliability.

• Calibration with a standard irradiance source
• Supports spectroradiometer measurement consistency
• Useful for laboratory and quality control workflows
• Helps improve traceability and repeatability