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Combined Interpretations of the 2003, 2009, and 2016 Standards that apply to Volume 1 of the 2016 TNI Standard


Question:  I'm trying to determine if the weight sets used to verify balances prior to use MUST be Class 1.

TNI Response:  A laboratory may use any class to verify the balance if the weights are traceable to a national standard. A Class 1 (or "S") weight is normally considered a reference standard, but may be used as a working standard. If the laboratory has designated the weight as a reference standard, the weight may only be used for calibration (i.e. calibrating/checking working standards). Standards that are used for daily calibrations ( must be traceable to a national standard. The Class1 or “S” weights can be used to verify the working standards, since these are traceable to NIST.