Those familiar with electricity meters know that conventional AC meters are straightforward to wire: simply connect them to single-phase or three-phase AC mains, and they operate normally without requiring any additional auxiliary power supply.

The core reason is that, for example, China's domestic mains supply provides a stable AC 220V voltage — the value is constant with minimal fluctuation. The meter can directly tap power from the measurement voltage, converting it to supply its own internal mechanism and metering chip, which is entirely sufficient to meet its self-power needs.

However, many practitioners who encounter DC electricity meters for the first time often have the same question:

❓ Why do most DC electricity meters require a separate auxiliary power supply?

Recently, a customer raised exactly this issue. Their site operating voltage was 13–220V with a current of 10A. When integrating our DJZ1226 DC energy meter, they were puzzled by the design requirement for an external auxiliary power supply.

✅ The answer: This is actually determined by industry characteristics — what seems self-evident to insiders can easily cause cognitive confusion for outsiders. By examining the actual operating conditions and device principles, we can clearly understand the reasons.

First, the metering voltage range of DC energy meters is extremely wide. Take the DJZ1226 DC energy meter used in this consultation as an example: its adaptable metering voltage range is 10–1000V, covering everything from low to high voltage DC scenarios. However, the internal chips and circuits of the meter operate at fixed voltages and cannot accommodate such a broad voltage range. If power were taken directly from the measurement circuit, under low voltage conditions the supply would be insufficient, while under high voltage it would directly burn out the device — making stable operation impossible.

📂 To suit different markets and scenarios

The auxiliary power supplies of mainstream DC energy meters are standardized. For the domestic market, Reallin's DC meters use a DC 10–30V auxiliary power supply; for international models, a DC 9–36V wide-range auxiliary power supply is adopted. These meters are primarily used in DC charging piles, photovoltaic energy storage, DC distribution, and similar scenarios — and these sites are typically equipped with standard DC 12V or DC 24V regulated power supplies, which can easily provide stable power to the meter.

In addition, there are also models that accommodate special scenarios. Some DC energy meters can support AC 220V mains as an auxiliary power supply, offering greater flexibility depending on the site's power conditions.

On the other hand, the core logic behind why AC meters do not need an auxiliary supply is that their measurement voltage is fixed with minimal fluctuation, allowing self-powering through voltage conversion. By contrast, DC supply scenarios have enormous voltage spans. Currently, mainstream DC charging piles operate in the range of 200–750V, new models reach 200–950V or even 1000V, and the latest ultra-fast chargers are iterating toward 1500V high voltage.

📝 Summary

Such a wide-span high-voltage DC metering scenario simply cannot power the meter from its own measurement voltage. Therefore, all high-voltage, wide-range DC energy meters must be equipped with an independent auxiliary power supply to ensure accurate metering and stable operation.