ML2439A USB Power Meter User Guide : General Information : Calibration and Verification
 
Calibration and Verification
The Power Meter comes fully calibrated from the factory and there are no field-adjustable components. Anritsu recommends annual calibration and performance verification by local Anritsu service centers.
Identification Number
The ML2439A identification number is affixed to the rear panel. Please use the complete ID number when corresponding with the Anritsu Customer Service department.