1. Introduction
The EASTRON SDM120CT-40mA is a single-phase multi-function DIN rail energy meter designed for accurate measurement of active energy, reactive energy, current, voltage, power, power factor, frequency, and other parameters. It is suitable for monitoring energy consumption in various applications, including residential, solar PV systems, industrial settings, and utility applications.
This meter is designed to work with a wide range of Current Transformers (CTs), providing flexibility in its operation. It features two pulse outputs and one Modbus communication port for remote monitoring and configuration.
Figure 1: EASTRON SDM120CT Energy Meter with TA16 100A/40mA Current Transformer
Video 1: Product overview showing the SDM120CT meter from various angles and its components.
2. Key Features
- Compact 1 module (18mm) width for DIN rail mounting.
- Equipped with 2 Pulse Outputs for energy monitoring and Modbus communication for remote data access.
- Supports bi-directional measurement, suitable for both consumption and generation monitoring (e.g., solar PV).
- Clear LCD display with backlighting for easy readability in various lighting conditions.
- Operates with a 40mA Current Transformer (CT).
- Multi-measurement capabilities: kWh (kilowatt-hour), W (watt), V (volt), A (ampere), PF (power factor), Hz (frequency), dmd (demand), etc.
- Designed for 1 Phase 2 Wire (1P2W) electrical systems.
Figure 2: Product features, wiring diagram, and dimensions.
3. Setup and Installation
Safety First: Installation should only be performed by qualified personnel in accordance with local electrical codes and regulations. Ensure power is disconnected before beginning any installation work.
3.1 Mounting
The SDM120CT is designed for DIN rail mounting. Securely attach the meter to a standard 35mm DIN rail within an appropriate electrical enclosure.
3.2 Wiring
Refer to the wiring diagram below (Figure 3) for correct electrical connections. The meter requires connection to the main power supply and the external Current Transformer (CT).
- Power Supply (L, N): Connect the live (L) and neutral (N) wires of the single-phase supply to the designated terminals on the meter. The rated voltage is 230V AC.
- Current Transformer (CT): Connect the secondary output of the 40mA CT to the corresponding input terminals on the meter. Ensure the CT is installed correctly around the live wire of the circuit to be measured, observing the direction of current flow if indicated on the CT.
- Pulse Outputs: If using pulse outputs for external monitoring, connect them to your data acquisition system.
- RS485 Modbus: For remote communication, connect the RS485 A and B terminals to your Modbus network. Ensure proper termination and addressing for the Modbus network.
Figure 3: Wiring Diagram and Dimensions. The wiring diagram shows connections for L, N, CT, and RS485 Modbus.
4. Operating Instructions
4.1 Power On and Display
Once correctly wired and power is applied, the meter's LCD display will illuminate. The backlit display ensures clear visibility of measurements.
Figure 4: Close-up of the meter's LCD display and terminals.
4.2 Reading Measurements
The meter cycles through various measurement parameters on its LCD display. These typically include:
- Total Active Energy (kWh)
- Instantaneous Active Power (W)
- Voltage (V)
- Current (A)
- Power Factor (PF)
- Frequency (Hz)
- Demand (dmd)
- Reactive Energy (kVArh)
Consult the full product datasheet for details on navigating the display and accessing specific parameters.
4.3 Modbus Communication
The integrated RS485 Modbus port allows for remote reading and configuration of the meter. This requires a Modbus master device (e.g., PLC, HMI, or computer with Modbus software) and knowledge of the Modbus protocol. Refer to the Modbus protocol instruction and register map for detailed communication setup.
5. Maintenance
The EASTRON SDM120CT is designed for long-term, maintenance-free operation. However, periodic checks are recommended:
- Cleaning: Keep the meter's display and casing clean using a soft, dry cloth. Do not use abrasive cleaners or solvents.
- Connections: Periodically inspect all wiring connections to ensure they are secure and free from corrosion.
- Environment: Ensure the operating environment remains within the specified temperature and humidity ranges to prevent damage.
No user-serviceable parts are inside the meter. Do not attempt to open or repair the device, as this will void the warranty and may pose a safety risk.
6. Troubleshooting
If you encounter issues with your SDM120CT meter, consider the following:
- No Display/Power:
- Check the main power supply to the meter.
- Verify all power connections (L and N terminals) are secure.
- Incorrect Readings:
- Ensure the Current Transformer (CT) is correctly installed and oriented.
- Verify the CT's secondary output is properly connected to the meter.
- Check for loose wiring connections.
- Modbus Communication Failure:
- Verify RS485 A and B connections are correct (polarity).
- Check Modbus address and baud rate settings on both the meter and the master device.
- Ensure proper termination resistors are used on the Modbus network if required.
- Consult the Modbus protocol instruction for detailed troubleshooting steps.
If problems persist, contact technical support for assistance.
7. Specifications
| Attribute | Value |
|---|---|
| Model Number | SDM120CTM 100mA |
| Dimensions | 90*67.5*17.5mm |
| Phase | Single Phase |
| Rated Voltage | 230V |
| Output Voltage | 220V |
| Power Supply | AC |
| Max Operating Current | 19A & Under |
| Secondary Input | 40mA |
| Accuracy Class | Class 1 |
| Measuring Energy Range | 99999.9 kWh |
| Frequency | 50/60Hz (±10%) |
| Display Type | Digital Only |
| Display | LCD with backlit |
| Operating Temperature | -25℃ to 55℃ |
| Overcurrent withstand | 30Imax for 0.01s |
| AC voltage withstand | 4KV for 1 minute |
| Starting current | 0.4% of Ib |
| Certification | CE |
| DIY Supplies | Electrical |
| Battery Included | No |
| High-concerned chemical | None |
| Origin | Mainland China |
Figure 5: Product Certifications.
8. Warranty and Support
8.1 Warranty
This product comes with an 18-month warranty from the date of purchase, covering manufacturing defects. Please retain your proof of purchase for warranty claims.
8.2 Technical Support
For technical inquiries, datasheets, Modbus protocol instructions, or Modbus register maps, please visit the official Eastron website: www.eastrongroup.com. You can also contact customer service for further assistance.
9. User Tips
- Inverter Compatibility: If integrating with a solar PV system, verify compatibility with your specific inverter brand (e.g., Growatt) by checking the inverter's documentation or contacting Eastron support.
- Modbus Integration: The meter's RS485 Modbus communication is a powerful feature for advanced monitoring. Ensure you have the correct Modbus protocol instruction and register map for seamless integration with your system.
- Voltage Requirement: This meter is designed for 220V/230V systems. Confirm your electrical system's voltage matches the meter's specifications before installation.
