# Selection & Specs

> Help users understand hardware capabilities and version differences before purchasing or upon first receiving the product.

### ⚡ Quick Answers

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<summary><strong>What communication protocols do your devices support?</strong> <code>[All Products]</code></summary>

We offer multiple options based on a flexible dual-chip architecture to fit different systems:

* Wi-Fi: Typically available as Open Wi-Fi (BLE + Wi-Fi with open APIs like MQTT/HTTP for integrators and DIYers) or Tuya Wi-Fi (easy use via the Smart Life app).
* Zigbee: Choose Standard Zigbee 3.0 (open integration for integrators and DIYers) or Tuya Zigbee.
* LoRaWAN: Ideal for long-range transmission in commercial buildings, factories, and infrastructure.
* Modbus RTU: For scenarios demanding maximum stability and reliability, such as industrial environments.

Please check the specific product pages to see the supported protocols for each product line.

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<summary><strong>What is the maximum wire diameter for the SPM01 and SPM02?</strong>  <code>[SPM01/SPM02 Products]</code></summary>

The SPM01 and SPM02 feature a pass-through design with a Ø9.6mm hole. It can accommodate wires up to 4 AWG (or standard 16mm²), which perfectly matches its 63A maximum current rating.

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<summary><strong>Can I use third-party CTs with the SDM series?</strong> <code>[SDM Products]</code></summary>

While technically possible, we **do not recommend** using third-party CTs if you require high measurement accuracy.

Every SDM meter is shipped as a complete set. The main unit and its matched CTs are factory-calibrated and tested together to guarantee **Class 1 accuracy** (compliant with IEC 61557-12). Using third-party CTs means this accuracy can no longer be guaranteed.

**⚠️ Important Safety Warning:** If you still choose to use third-party CTs, you must strictly check the CT's secondary output current. Exceeding the meter's maximum rated input will permanently damage the device. For example, the maximum CT input current for the **SDM01** is **83.3mA**.

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<summary> <strong>What Apps and Gateways/Hubs do your products support?</strong> <code>[All Products</code></summary>

Compatibility depends on the specific communication connectivity of the device you choose:

<table><thead><tr><th width="172">Connectivity</th><th width="262">App</th><th>Hub / Gateway</th></tr></thead><tbody><tr><td><strong>Tuya Wi-Fi</strong></td><td>Smart Life (or any official Tuya ODM app based on the Tuya App SDK)</td><td>None required — connects directly to Tuya Cloud via Wi-Fi router</td></tr><tr><td><strong>Tuya Zigbee</strong></td><td>Smart Life (or any official Tuya ODM app based on the Tuya App SDK)</td><td>Requires a Tuya Zigbee Gateway<sup>1)</sup></td></tr><tr><td><strong>Open Wi-Fi</strong></td><td>Our BT Power Link app; BLE API is open for custom app integration. Via open local LAN and cloud APIs, theoretically any customer-specific app or platform can be integrated</td><td>None required — connects via Wi-Fi router</td></tr><tr><td><strong>Standard Zigbee 3.0</strong></td><td>Any compatible app via your chosen gateway</td><td>Any universal Zigbee hub/gateway<sup>2)</sup></td></tr><tr><td><strong>LoRaWAN</strong></td><td>Your own system or app</td><td>Any LoRaWAN Gateway + Network Server</td></tr><tr><td><strong>Modbus RTU</strong></td><td>Your integrated software system</td><td>Any Modbus Master device (e.g., PLC, RTU, Gateway)</td></tr></tbody></table>

**📝 Notes:**

1. **Tuya Zigbee + Zigbee2MQTT:** Technically possible for DIY use, but **not recommended for large-scale commercial deployments** due to stability issues (e.g., Zigbee network storms caused by how data packets by Tuya's Zigbee firmware) and potential security risks (e.g. No installation code used). For open integration, choose **Standard Zigbee 3.0** instead.
2. **Standard Zigbee 3.0 Gateways:** Please note that while there are many Zigbee gateways available for building system integrators (such as the [SMHUB Nano Hub](https://smartlight.me/smart-home-devices/zigbee-devices/smhub-nano)), many smart home hub with Zigbee gateway feature actually have limited openness for third-party device integration. We highly recommend confirming compatibility before purchase. Smart home hub we have officially verified include Home Assistant, SmartThings, and Homey.

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<summary><strong>Which circuit breakers are compatible with the SPM01/02 energy sensors?</strong> <code>[SPM Products]</code></summary>

Compatibility depends on the installation variant you choose. **If you are unsure about compatibility, we highly recommend choosing the Flexible version.**

* **Flexible / "Hanging-on-cable" Version (Universal & Recommended):** Fits **all brands** of circuit breakers. It is installed by simply hanging on the phase line that passes through the sensor's hole, making it universally compatible regardless of the breaker's design.
* **"Miniature-Circuit-Breaker-Mounting" (MCBM) Version:** Requires specific matching because terminal designs and housings vary across different manufacturers.
  * **Officially Verified:** Fully verified for compatibility (wiring capacity, thermal performance, and mechanical fit) with the Siemens 5SY / 5SL series.
  * **Other Brands:** While we have seen successful user installations with models such as Eaton PL9, ABB SH200, and Hager MC, these have not been officially tested or verified by our team. Due to the vast variety of breakers on the market, we cannot officially guarantee compatibility for unverified models.

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<summary><strong>Can the SPM/SDM monitor direct current (DC)?</strong> <code>[SPM/SDM Products]</code></summary>

No, both the SPM and SDM series are designed exclusively for **alternating current (AC)** monitoring and cannot measure direct current (DC).

Currently, we do not offer any DC measurement devices, and please note that there are no plans to introduce DC products in our 2026 product roadmap.

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<summary><strong>Can the SPM meters be flashed with custom firmware?</strong> <code>[SPM Products]</code></summary>

Technically yes, but **only for the Open Wi-Fi and Standard Zigbee versions**. It is not possible to flash custom firmware onto the Tuya Wi-Fi or Tuya Zigbee versions.\
\
**Technical Background:** For users wondering if they can flash Standard/Open firmware onto Tuya hardware, this will not work because the internal hardware architecture and UART communication logic are completely reversed between the two variants:

* **Tuya Wi-Fi & Tuya Zigbee Versions:** The internal MCU acts as the **master**. It controls the communication SoC (System on a Chip) via UART using the Tuya SDK to handle communications.
* **Open Wi-Fi & Standard Zigbee Versions:** The communication SoC acts as the **master**. It actively reads the MCU's register addresses via UART to obtain the energy data.

Because of this fundamental difference in the master-slave relationship, simply flashing standard firmware onto Tuya connectivity hardware will not make it function.

⚠️ **Safety Warning:** We strongly advise against physical modifications or flashing custom firmware. The device contains high-voltage circuits that pose serious safety risks during modification.

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### 🛠️ Detailed Guides


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