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


(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.
(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.
(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.
(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.
(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.
TABLE 1
Influence quantities
Reference value
Tolerance
Ambient temperature
Reference temperature or, if not indicated, 23°C.
>15°C to <30°C
Meter position
Vertical
±3°
Voltage
Reference voltage
±1.5%
Frequency
Reference frequency 50Hz
±0.5%
Voltage and current waveform
Sinusoidal form
Distortion factor <5%
External magnetic induction at the reference frequency (paragraph 5.4)
Zero
Induction value that does not produce a relative error variation of more than& ±0.3%
TABLE 2
Test load in terms of marked current
Test No. & load
Power factor
Basic/maximum
Maximum continuous
Long range
Short range
Meter type
Polyphase meter load
Note 1 Where a range is given, any value within that inclusive range may be selected.
Note 2 For maximum continuously rated prepayment meters, the low load test value may be twice the value shown.
Note 3 For test no. 4 & 6, the inductive power factor shall be between 0.45 and 0.55 inclusive.
1 (high)
1
Imax
100%
100%–200% (Note 1)
100%–125% (Note 1)
Single & polyphase
Balanced
2 (intermediate)
1
Ib or 125%IB
Any load between 25%–75% of the value specified for Test No. 1
Single & polyphase
Balanced
3 (low)
1
5%Ib
1.67% (note 2)
5%
5%
Single & polyphase
Balanced
4 (inductive)
0.5
Ib or Imax
100%
The same value selected for Test No. 1
Single & polyphase
Balanced
5 (element)
1
Ib
100%
The same value selected for Test No. 1
Polyphase
One phase loaded in turn
6 (inductive) (element)
0.5
Ib
100%
The same value selected for Test No. 1
Polyphase
One phase loaded in turn

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Source: https://www.legislation.gov.uk/uksi/1990/792/schedule/3/paragraph/9 (the official version)
Page: https://openlegislation.uk/meters-certification-regulations-1990/schedule-3/paragraph-9
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.