{
  "url": "https://openlegislation.uk/meters-certification-regulations-1990/schedule-3/paragraph-9",
  "json_url": "https://openlegislation.uk/meters-certification-regulations-1990/schedule-3/paragraph-9.json",
  "legislation": "uksi/1990/792",
  "legislation_title": "The Meters (Certification) Regulations 1990",
  "legislation_url": "https://openlegislation.uk/meters-certification-regulations-1990",
  "path": "schedule/3/paragraph/9",
  "kind": "paragraph",
  "number": "9",
  "heading": "Margins of error",
  "text": "(1) The maximum error permitted for single and polyphase whole current meters and for single and polyphase transformer operated meters, when tested with transformers connected, shall not exceed plus or minus 1.9% for tests 1, 2, 3 and 4 given in Table 2.\n(2) The maximum error permitted for both single phase and polyphase transformer operated meters, when tested without transformers connected, shall not exceed plus or minus 1.4% for tests 1, 2, 3 and 4 given in Table 2.\n(3) For polyphase whole current and transformer operated meters, when tested with transformers connected, the maximum error shall not exceed plus 2% or minus 3% for tests 5 and 6 given in Table 2.\n(4) For polyphase whole current and transformer operated meters, when tested without transformers connected, the maximum error shall not exceed plus 1.5% or minus 2.5% for tests 5 and 6 given in Table 2.\n(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.\nTABLE 1\nInfluence quantities\nReference value\nTolerance\nAmbient temperature\nReference temperature or, if not indicated, 23°C.\n>15°C to <30°C\nMeter position\nVertical\n±3°\nVoltage\nReference voltage\n±1.5%\nFrequency\nReference frequency 50Hz\n±0.5%\nVoltage and current waveform\nSinusoidal form\nDistortion factor <5%\nExternal magnetic induction at the reference frequency (paragraph 5.4)\nZero\nInduction value that does not produce a relative error variation of more than& ±0.3%\nTABLE 2\nTest load in terms of marked current\nTest No. & load\nPower factor\nBasic/maximum\nMaximum continuous\nLong range\nShort range\nMeter type\nPolyphase meter load\nNote 1 Where a range is given, any value within that inclusive range may be selected.\nNote 2 For maximum continuously rated prepayment meters, the low load test value may be twice the value shown.\nNote 3 For test no. 4 & 6, the inductive power factor shall be between 0.45 and 0.55 inclusive.\n1 (high)\n1\nImax\n100%\n100%–200% (Note 1)\n100%–125% (Note 1)\nSingle & polyphase\nBalanced\n2 (intermediate)\n1\nIb or 125%IB\nAny load between 25%–75% of the value specified for Test No. 1\nSingle & polyphase\nBalanced\n3 (low)\n1\n5%Ib\n1.67% (note 2)\n5%\n5%\nSingle & polyphase\nBalanced\n4 (inductive)\n0.5\nIb or Imax\n100%\nThe same value selected for Test No. 1\nSingle & polyphase\nBalanced\n5 (element)\n1\nIb\n100%\nThe same value selected for Test No. 1\nPolyphase\nOne phase loaded in turn\n6 (inductive) (element)\n0.5\nIb\n100%\nThe same value selected for Test No. 1\nPolyphase\nOne phase loaded in turn",
  "extent": null,
  "status": null,
  "version": "current",
  "annotations": [],
  "outstanding_effects": [],
  "provenance": {
    "source": "legislation.gov.uk",
    "source_url": "https://www.legislation.gov.uk/uksi/1990/792/schedule/3/paragraph/9",
    "retrieved_at": "2026-10-29T15:22:08.525435+00:00"
  },
  "licence": "Open Government Licence v3.0",
  "licence_url": "https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/",
  "attribution": "Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives."
}