Calibration Weights are certified to be used to ensure that scales or balances are giving you accurate readings. Calibration weights are assigned a class which is based on the accuracy or tolerance of the weight.
OIML: The Organisation Internationale de Métrologie Légale or International Organization of Legal Metrology (OIML) is an intergovernmental organization that provides standards and systems with the goal of harmonizing legal metrology procedures. From lowest (most accurate) to highest tolerance, OIML has classified the Calibration Weights in accuracy classes as E1, E2, F1, F2, M1, M2, and M3.
The following tables shows the tolerance levels for the different classes of weights, as per OIML.:
Certifications of Weights
While browsing Calibration Weights, you might come across mentions of certifications. Indeed, depending on your application, you may require that your calibration weights come with a certificate confirming that the lab testing the weights is accredited.
ISO/IEC 17025: The International Organization for Standardization (ISO) is an independent non-governmental organization comprising a membership of 164 national standards bodies. The International Electrochemical Commission (IEC) is an international standards organization for electrotechnical fields. Together with other liaison organizations, they created the ISO/IEC 17025 standards. This is the international reference to be used by testing and calibration laboratories that want to display their ability to provide reliable results.