# The Measuring Instruments Regulations 2016, Paragraph 3: MPEs


The effects of the various measurands and influence quantities (a, b, c,…) are evaluated separately, all other measurands and influence quantities being kept relatively constant at their reference values. The error of measurement, that shall not exceed the MPE stated in Table 2, is calculated as:
When the meter is operating under varying-load current, the percentage errors shall not exceed the limits given in Table 2.
Table 2
Operating temperatures
Operating temperatures
Operating temperatures
Operating temperatures
MPEs in percent at rated operating conditions and defined load current levels and operating temperature
Operating temperatures
Operating temperatures
Operating temperatures
Operating temperatures
+ 5 °C … + 30 °C
– 10 °C … + 5 °C
or
+ 30 °C … + 40 °C
– 25 °C … – 10 °C
or
+ 40 °C … + 55 °C
– 40 °C … – 25 °C
or
+ 55 °C … + 70 °C
Meter class
A
B
C
A
B
C
A
B
C
A
B
C
Single phase meter; polyphase meter if operating with balanced loads
Imin ≤ I < Itr
3.5
2
1
5
2.5
1.3
7
3.5
1.7
9
4
2
Itr ≤ I < Imax
3.5
2
0
4.5
2.5
1
7
3.5
1.3
9
4
1.5
Polyphase meter if operating with single phase load
Itr ≤ I < Imax
, see exception below
4
2.5
1
5
3
1.3
7
4
1.7
9
4.5
2
For electromechanical polyphase meters the current range for single-phase load is limited to 5Itr ≤ I ≤ Imax
When a meter operates in different temperature ranges the relevant MPE values shall apply.
The meter shall not exploit the MPEs or systematically favour any party.

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Source: https://www.legislation.gov.uk/uksi/2016/1153/schedule/1E/paragraph/3 (the official version)
Page: https://openlegislation.uk/measuring-instruments-regulations-2016/schedule-1E/paragraph-3
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.