The accuracy grade and allowable error of flowmeter within the specified flow range shall meet the requirements of Table 1. The meter error indicates the relative indication error. For the indication of flowmeter error for instantaneous flow indication, reference error can also be used. The allowable error series shall conform to the provisions of Table 1. The accuracy grade will not be given in the tender document of the verification result, but the allowable error expression shall be used, and FS shall be marked after the allowable error, such as ± 0.5% FS.

In the primary verification of a flowmeter, the expression method of flowmeter error shall be given according to one of accuracy grade and reference error; for the flowmeter using the combination of relative indication error and reference error to express the error, a unified method shall also be used in the primary verification to indicate the error.