Discussion on System Error Caused by
Power Meter Internal Resistance
Even when electrical appliances are plugged into sockets and in a powered-off or standby mode, they still consume electricity. Considering the amount of electrical devices in households and offices worldwide, reducing the power consumption in these non-operating modes is a key strategy for energy conservation.
The International Energy Agency (IEA) introduced the 1-Watt Initiative in 1999, with the goal of ensuring, through international collaboration, that by 2010, the power consumption of all newly sold household appliances in standby mode would be limited to 1 watt or less. By 2013, the objective was to further reduce the Initiative goal to 0.5 watts.
This Initiative has also become the laws and regulations in many countries and regions. With the evolution of energy-saving technologies, the latest regulation from the European Union on Energy-Related Products (ErP), EU Regulation 2023/826 officially came into effect in 2023 and will be enforced on May 9, 2025. This regulation replaces the 2008 regulation (EC) No.1275/2008. The revisions in the new regulation aim to update ecological design requirements based on technological advancements. In short, the regulations are wider and stricter.
Wider regulation coverage: Expanding the scope of regulated products
- Electric furniture and electrically powered building equipment, such as electric doors, electric windows, electric blinds, and electric curtains.
- Products equipped with low-voltage (below 6V) external power supply.
- Standby power consumption of portable battery-powered products with charging circuits after the battery is fully charged.
- Printers other than 3D printers.
- Simple set-top boxes.
The annual sales volume of both existing and newly regulated devices is estimated to be around 8 billion units. There are an estimated 5 billion products in use in the EU.
Stricter regulations:
The non-operating power consumption of electrical appliances is divided into: off mode; standby mode; Networked standby mode. Table 1 shows the regulatory requirements for the two phases in 2025 and 2027 respectively.
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Energy efficiency requirements |
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Mode |
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From 2025-5-9 |
From 2027-5-9 |
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Off mode |
|
≤0.50W |
≤0.3W |
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Standby mode |
Without display |
≤0.50W |
|
|
With display |
≤1.00W (Household tumble driers) ≤0.80W (Others) |
||
|
Networked standby mode |
HiNA equipment |
8.00W |
7.00W |
|
Others |
2.00W |
||
Table 1: Energy efficiency requirements of new regulations
Devices with high network availability (HiNA): including routers, switches, hubs, modems, wireless access points, Voice over Internet Protocol (VoIP) or video phones, etc. Devices that use routers, switches or wireless access points as secondary (collateral) functions, such as composite set-top boxes, are also HiNA.
Devices with low network availability (LoNA) or other network connected devices: includes all other network connected devices.
The EU estimates that the new laws and regulations will achieve energy savings
by 2030
- Annual electricity consumption will be reduced by approximately 32.5 terawatt hours.
- Carbon dioxide emissions will be reduced by 4.6 million tons per year.
- Consumers will save 7 billion euros on electricity bills.
IEC62301 requirements for test and measurement equipment:
IEC 62301 is an international standard for testing and measuring the standby power consumption of household appliances. The test and measurement equipment recommended by it must at least meet the following parameters.
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Specification requirements |
GPM-8213 |
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Power resolution less than or equal to 1mW |
Conformed |
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Equipped with time integrator function |
Conformed |
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The power resolution is less than or equal to 1mWh, and the cumulative time resolution is less than or equal to 1 second |
Conformed |
|
Crest factor is greater than or equal to 3 |
Conformed |
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Minimum current range is less than or equal to 10mA. |
Conformed |
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Active power consists of AC and DC components. |
Conformed |
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Equipped with over-range automatic alarm function |
Conformed |
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The auto-ranging function can be turned off |
Conformed |
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Harmonic bandwidth is greater than or equal to 2.5kHz |
Conformed |
Table 2: IEC 62301 requirements for power meters measuring standby power consumption
Figure 2: GW Instek GPM-8213
Why is GW Instek GPM-8213 power meter the first choice for measuring standby power consumption?
The internal components of a power meter consist of a voltage meter and a current meter that first measure voltage and current, respectively, and then calculate power. In addition to meeting the above requirements of IEC62301, GPM-8213 also minimizes the system error caused by the internal resistance of the voltmeter and ammeter.
Test and measurement connection methods and system error:
Since the signal measured by standby power consumption has low power and low current characteristics, in addition to having a suitable measurement range, the digital power meter must have correct measurement connection, which is also the key to successful measurements. As shown in Figure 3, when measuring, a voltmeter is connected in parallel and an ammeter is connected in series to measure power consumption.
Figure 3(a) connects the voltmeter in parallel and is close to the DUT. At this time, the current value obtained by the ammeter is the sum of the voltmeter and the DUT, and the error caused by the voltmeter has little impact on the power consumption measurement of several watts. However, compared to the standby power consumption of 300~800 mW, the impact is huge.
Figure 3(b) the voltmeter is connected in parallel and is close to the power supply, the current value obtained by the ammeter only comes from the DUT. Even the internal resistance of the ammeter will cause measurement errors, but its impact is just a drop in the ocean that can almost be omitted.
Most European countries are gradually adjusting the voltage to 230 V and 400 V. Taking these two voltages and the 0.3W off mode required by the 2027 regulations as an example to calculate the impact of system errors on measurements.
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 |
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Power loss calculation: by 230V input GPM-8213 = (230V)2/2.4MΩ=22.04mW Y Brand = (230V)2/2MΩ=26.45mW V Brand = (230V)2/1MΩ=52.9mW
Power loss calculation: by 400V input GPM-8213 = (400V)2/2.4MΩ=66.67mW Y Brand = (400V)2/2MΩ=80mW V Brand = (400V)2/1MΩ=160mW |
Power loss calculation: by 0.3W/230V=1.3mA input GPM-8213 = (1.3mA)2x500mΩ=845μW Y Brand = (1.3mA)2x500mΩ=845μW V Brand = (1.3mA)2x600mΩ=1.014mW
Power loss calculation: by 0.3W/400V=750μA input GPM-8213 = (750μA)2x500mΩ=0.281μW Y Brand = (750μA)2x500mΩ=0.281μW V Brand = (750μA)2x600mΩ=0.337μW |
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Figure 3(a) Connection method and system error of general power consumption measurement |
Figure 3(b) Connection method and measurement error of standby power consumption measurement |
To learn more about the product information of GW Instek GPM-8213 (single phase) digital power meter, please go to GPM-8213:
https://www.gwinstek.com/en-global/products/detail/GPM-8213
Figure 4: GW Instek has a complete power measurement product portfolio:
Single-phase digital power meter (GPM-8213 on the left/GPM-8310 in the middle), three-phase digital power meter (GPM-8330 on the right)
References:
- Wikipedia https://en.wikipedia.org/wiki/One_Watt_Initiative
- EU website https://commission.europa.eu/energy-climate-change-environment/standards-tools-and-labels/products-labelling-rules-and-requirements/energy-label-and-ecodesign/energy-efficient-products/mode-standby-and-networked-standby-devices_en
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