# The Meters (Certification) Regulations 1990, Paragraph 9: Margins of error


(1) The maximum error permitted for both single phase and polyphase whole current and transformer operated meters, tested with transformers connected, shall not exceed plus or minus 1.5% for tests 1, 2, 3 and 4 given in Table 2.
(2) The maximum error permitted for both single phase and polyphase transformer operated meters, tested without transformers connected, shall not exceed plus or minus 1.0% for tests 1, 2, 3 and 4 inclusive given in Table 2.
(3) For polyphase whole current and transformer operated meters, tested with transformers connected, the maximum error shall not exceed plus 1.7% or minus 2.7% for tests 5 and 6 given in Table 2.
(4) For polyphase transformer operated meters, tested without transformers connected, the maximum error shall not exceed plus 1.2% or minus 2.2% for tests 5 and 6 given in Table 2.
(5) Where current and voltage transformers, which are intended to be used with meters, are not tested connected to a meter then the total error of the transformers at any load point throughout the rated range shall not exceed 0.5%; unless by matching transformers to meters enables the total error of meter and transformers to meet the requirements of paragraphs 9(1), 9(2), 9(3) and 9(4) above.

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Source: https://www.legislation.gov.uk/uksi/1990/792/schedule/1/paragraph/9 (the official version)
Page: https://openlegislation.uk/meters-certification-regulations-1990/schedule-1/paragraph-9
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.