No Load Test for Energy Meters 2020

With publishing of the Edition 2 of IEC62052-11 the minimum run time calculation formula has changed. This formula applies to all meters type tested after July 2020.
For meters with an earlier type test certificate the old calculation applies.

The purpose for this test is to make sure that the energy register is not start counting without the flow of load current. The current taken from e.g. the internal power supply shall not cause the meter to start registering energy.

The meter is allowed to give maximum one pulse on the pulse output.


Δt = minimum test time (minutes)
k = meter constant (imp/kWh)
m = number of elements
UTest = 1.1 Un (V)
Istart = meter starting current (A)

If you feel like having seen this formula before, you are right. The EN50470-3 is using this calculation for MID meter type test approval since the year 2006. The only difference is that the EN50470-3 is using for UTest = 115% Un.
I thank the IEC committee for almost perfect alignment.

Comparison Calculator

Minimum Required Time for No-Load Test
Nominal voltage
Starting current
Meter constant
Minimum test time IEC
Minimum test time EN

Nevertheless, this testing time is the absolute minimum. A metrological institute or type test facility will always at least double the time. The minimum test time is used for routine tests at manufacturers to utilize the test equipment most efficient.

Thank you for taking a look and “Happy Testing”

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