Genuine 3 year calibration validity
The International Bureau of Weights and Measures (BIPM) recommends that current measuring devices (such as optical power meters) should be calibrated at least annually to maintain calibration traceability to ISO17025.
However, this Kingfisher instrument has a unique power meter internal architecture. Two internal current references continuously calibrate the current measuring circuits, so calibration interval is extended and is limited by the need to recalibrate the optical detector. Additionally, the A/D converter is inherently monotonic, and there is no range changing.
The reference current stability specification over 3 years is > 20x better than is required to maintain the stated accuracy.