Hi Everyone, I'm implementing ISO 9001:2015 (with the aim for certification) at a company that sells automotive batteries. We offer 18 months warranty for our batteries. Part of the warranty process is validation of battery which we use a hydrometer and a multimeter to test. Therefore I am telling the manager that these devices need to be calibrated according to 188.8.131.52. For us to calibrate these devices we would need to send it to another country. I do not have a technical background in calibration, so I was wondering if we can calibrate our hydrometer internally (developing a test method with the related retained documented information) using the steps in the link below? https://www.wikihow.com/Calibrate-a-Hydrometer#Calibrating_a_Hydrometer_sub Feedback appreciated, calibration is not my area of expertise at all. Suraiya.