# Data & Measurement
> Explain where the data displayed in the App comes from, how often it refreshes, and where it is stored.
### ⚡ Quick Answers
What accuracy standard do your meters follow? [SPM/SDM Products]
Both SPM and SDM comply with [**IEC 61557-12**](https://webstore.iec.ch/publication/65510), the international standard specifically designed for **Power Metering and Monitoring Devices (PMDs)** — covering active power, reactive power, power factor, and energy measurement accuracy in a unified framework.
This is distinct from IEC 62053, which applies to traditional utility billing meters. IEC 61557-12 is more appropriate for compact, embedded monitoring devices like SPM and SDM, and is increasingly adopted across the industry for this class of product.
> 📖 For a deeper dive, the blog post "Understanding the IEC 61557-12 Standard That Makes Meter Comparisons Easier-[Part 1](https://blog.se.com/energy-management-energy-efficiency/energy-regulations/2016/10/18/understanding-iec-standard-makes-meter-comparisons-easier/) and [Part 2](https://blog.se.com/energy-management-energy-efficiency/energy-regulations/2016/10/27/understanding-iec-standard-makes-meter-comparisons-easier-part-2/)", written by [Mr Franck Gruffaz](https://blog.se.com/author/franck-gruffaz/), is a good introductory material for the standard and its applications.
Why does the SPM/SDM show lower (or different) energy consumption compared to another meter?
Slight discrepancies are normal. If the difference is noticeable, it is typically due to one or more of the following:
**1. CT Installation Issues (SDM Only)** Ensure each clamp CT is fully snapped shut with no debris in the core gap — even a small gap causes flux leakage and lower readings.
**2. Calibration Accuracy vs. Consumer Smart Plugs** Consumer smart plugs are typically calibrated to a much looser tolerance than IEC Class 1, with errors more pronounced at low load levels.
**3. Limited DC Component Tolerance (vs. Modern Utility Billing Meters)** SPM uses miniature CTs; SDM uses clamp CTs — both have limited immunity to DC components in the AC waveform. Modern utility billing meters are specifically rated for DC offset handling. High-power single-phase inverter-driven loads (e.g., heat pumps, variable-frequency drives) can produce asymmetric current waveforms that cause mild CT saturation, resulting in slightly lower readings. This is a known physical limitation of this class of monitors.
**4. Low-Load / Standby Accuracy Range** If the monitored circuit runs mostly at very low standby power (average current below **Imin \~50mA**), readings may fall outside the specified accuracy range. A comparison in this range is not meaningful.
**5. Accuracy Class Differences** SPM02 and SDM full range comply with IEC Class 1 (±1%). Lower-class meters or smart pluggers (±2%\~±5%) will accumulate diverging errors over time, especially under reactive or mixed loads.
**6. Other Causes** The above covers the most common scenarios, but measurement discrepancies can sometimes stem from factors specific to your installation or load profile. If you've worked through the above and the difference remains unexplained, we're happy to investigate together — and if it points to something we can improve in the product, we'll take it seriously.
> 💡 **For a clean comparison:** Use a pure resistive load (e.g., 1000W heater) and compare **real-time Wattage**, not accumulated kWh.
How to download the historical data measured by SPM/SDM Meters (Tuya Version)?
Previously, exporting historical energy data from standard Tuya connectivity products required complex cloud API configurations or third-party platforms like Home Assistant.
To solve this, we have fully upgraded our Tuya connectivity product range—including both **Tuya Wi-Fi and Tuya Zigbee** versions—to the new **"Davidia" (Gongtong) firmware**.
If you are using a Davidia-version SPM/SDM meter, you can download your data directly through the Smart Life App with zero programming required:
* **One-Click Data Export:** Simply tap the download icon on the completely redesigned Historical Chart Page. Your historical bi-directional energy data will be sent directly to your email in a convenient spreadsheet format.
* **Per-Phase Data Support:** For 3-phase models, you can even export historical data for each individual phase independently, which is perfect for precise analysis.
> 📖 For a detailed UI guide and a full list of supported models featuring the data export function, please check out our [product update](https://shop.bituo-technik.com/blogs/tech-hub/product-update-energy-meters-using-tuya-wifi-module-now-support-bi-directional-data-export-email-delivery).
Tuya "Davidia" vs. "Basic" Version: What's the difference?
Scheduled for **May 1, 2026**, all electricity meters produced and delivered by our company using Tuya AIoT services will be upgraded to the new **'Davidia'** version.
The key differences between the Davidia version and the Basic version are as follows:
**1. New Features**
* **Data Export:** Added functionality to export historical energy data and send it directly via email in a convenient spreadsheet format (Excel/CSV).
* **Per-Phase Data Support (3-Phase Models):** Users can now export and email historical data for each individual phase independently, allowing for more precise load monitoring and analysis.
**2. Technical & UI Changes**
* **Optimized Firmware:** The Davidia version utilizes specific, upgraded communication module firmware and PIDs from Tuya.
* **User Interface:** The most noticeable difference for end-users is the App interface layout. The Davidia version features a redesigned Historical Chart Page and a brand-new Data Export Page.
**UI Comparison**
| Interface | Tuya "Davidia" Version | Tuya "Basic" Version |
| ------------------------- | --------------------------------------------------------- | -------------------------------- |
| **Historical Chart Page** | 
|  |
| **Data Export Page** |  | **Not Available** |
> 💡 **Note:** Some Davidia version units have already been sold prior to May 1, 2026. If you require the data export feature, please verify the firmware version with your vendor before purchase.
Does SPM/SDM support bi-directional energy measurement? [SPM/SDM Products]
Yes! Both our SPM and SDM series support bi-directional energy measurement. They can accurately monitor both the energy consumed from the grid and the surplus energy exported back to the grid (e.g., from solar panels).
Note: If your application requires high-speed local data transmission for real-time control—such as solar export limiting—we highly recommend choosing the SDM01 Combo Gen2 series, as its dedicated metering MCU can deliver stable power readings in under 150ms.
### 🛠️ Detailed Guides
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