Overview
The APM521 is a high-performance network power meter integrating full electrical measurement, high-precision energy metering, power quality analysis, event logging, and network communication.
Designed for comprehensive monitoring of critical power distribution systems, its modular structure supports flexible expansion with DI/DO, AO, second RS485, Ethernet, and other modules, making it an ideal data acquisition front-end for smart distribution, energy management, and industrial automation.
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Multi-Model Options
- Base unit with full measurement
- KC: 4DI + 2DO module
- KM: 4DI + 2DO + 2AO module
- CE: Ethernet communication module
- Log: MicroSD card recording module
- R: DIN rail mounting adapter
Wide Power Supply
- AC/DC 85-265V wide range
- ≤4W low power consumption
- Suitable for various industrial environments
High Accuracy
- Voltage/current: Class 0.2
- Active energy: Class 0.2S
- 2-63rd harmonics analysis
- ±1% harmonic accuracy
Standard Outputs
- RS485 Modbus-RTU
- 2 pulse outputs (active/reactive)
- Configurable alarm thresholds
- Event logging capability
Function
| Measurement | Power Quality | Energy & Demand | I/O & Alarms | Communication & Integration |
| Voltage: Phase, Line, Residual | Harmonics: 2nd-63rd, THD, Odd/Even | Four-quadrant Active/Reactive/Apparent | Digital Inputs: Up to 4 (NO/NC config) | Standard: 1x RS485, Modbus-RTU |
| Current: Phase, Neutral | Unbalance: Voltage, Current | Multi-tariff Energy: 4 tariffs, 14 periods | Digital Outputs: Up to 2 (alarm/remote) | Optional: 2nd RS485 or Ethernet (Modbus-TCP, FTP) |
| Power: Active/Reactive/Apparent (per phase + total) | Sequence: Pos/Neg/Zero | Demand Recording: Current/Power (with timestamp) | Analog Outputs: Up to 2 (4-20mA, etc.) | Protocols: Modbus-RTU, DL/T 645-2007, Modbus-TCP |
| Power Factor: per phase + total | Waveform: Real-time display | Extreme Value Statistics: Max/Min with timestamps | Alarms: 2 groups, 128+ alarm types | Data Logging: Optional MicroSD card |
| Frequency | Other: Peak coeff., K-factor | Frozen Energy: 24h/31d/12m/scheduled | Event Logging: 128 alarms + 128 DI/DO |
Specification
| Parameter | Specification |
| Input Voltage | Rated: AC 57.7/100V, 220/380V, 400/690V (L-N/L-L) Overload: 1.2× rated (continuous), 2× rated for 1s Burden: <1VA per phase |
| Input Current | Rated: 1A or 5A (via external CTs) Overload: 1.2× rated (continuous), 10× rated for 1s Burden: <0.2VA per phase |
| Measurement Accuracy | Voltage/Current: Class 0.2 Active Power/Energy: Class 0.2S (IEC 62053-22) Reactive Energy: Class 2 (IEC 62053-23) Frequency: ±0.2% |
| Harmonic Measurement | 2nd–63rd, accuracy: ±1% (for THD > 1%) |
| Response Time | ≤200ms for V, I, P; ≤1s for energy |
| Auxiliary Power | AC/DC 85–265V Power consumption: ≤4W, 10VA |
| Digital I/O (Optional) | KC Module: 4DI + 2DO KM Module: 4DI + 2DO + 2AO |
| Analog Output (Optional) | KM Module: 2 channels, 4-20mA (0-20mA configurable) Load capacity: ≤300Ω |
| Communication | Standard: 1x RS485 (Modbus-RTU) Optional: 2nd RS485 (Modbus-RTU) or Ethernet (Modbus-TCP, FTP) |
| Data Logging (Optional) | Log Module: MicroSD card slot for local data logging (configurable interval) |
| Pulse Output | 2 channels: Active & reactive energy pulses (configurable) |
| Operating Environment | Temperature: -40℃～+70℃ Humidity: ≤95% non-condensing Altitude: ≤2000m (≤5000m with limitations) |
| Safety & EMC | Dielectric strength: AC 4kV for 1min (comm. to inputs) EMC: Class IV (Electrostatic discharge, Fast transient burst, Surge) |
| Mounting | Panel mount (96×96mm cutout) or 35mm DIN rail (with R option) |
| Dimensions (W×H×D) | Panel mount: 96×96×50mm (without modules) DIN rail: 96×96×96mm (without modules) Modules: 86×86×30.5mm |
| Ingress Protection | IP54 (front panel), IP30 (body) |
| Standards Compliance | IEC 61010-1, IEC 61010-2-30, UL 61010-1, CAN/CSA C22.2, GB/T 17215.321-2021, etc. |
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Model Selection
| Model Code | Description |
| APM521 | Base unit with standard features (full measurement, 1x RS485, pulse output) |
| APM521/KC | Base unit + KC module: 4DI + 2DO |
| APM521/KM | Base unit + KM module: 4DI + 2DO + 2AO (4-20mA) |
| APM521/CE | Base unit + Ethernet module (Modbus-TCP, FTP) |
| APM521/Log | Base unit + Log module (MicroSD card logging) |
| APM521/R | Base unit with 35mm DIN rail mounting adapter (requires no other modules) |
Compatible Accessories
| Accessory | Description |
| Current Transformers | External CTs with secondary rating of 1A or 5A (e.g., AKH-0.66 series) |
| RS485 Repeater | For extending RS485 communication distance beyond 1000m |
| MicroSD Card | For data logging module, recommended capacity 2GB-32GB, formatted to FAT32 |
FAQ
The APM521/KC includes 4 Digital Inputs and 2 Digital Outputs (relay outputs). The APM521/KM includes the same 4DI+2DO but adds 2 Analog Outputs (4-20mA) for retransmitting measured parameters like current, voltage, or power to external analog systems.
The Ethernet module is a factory-installed option. It is recommended to order the /CE version directly. Retrofitting in the field is generally not supported due to internal hardware configuration.
Navigate to the “Input Setting” menu on the front panel. Select “U Rating1” for primary voltage (PT ratio) and “I Rating1” for primary current (CT ratio). The display will automatically show scaled primary values based on these settings. You can also configure these via Modbus registers (addresses 0x1015 for voltage, 0x1017 for current).
The meter has two independent alarm groups (Alarm1 and Alarm2). Each group can monitor over 80 different alarm types (see Alarm Table 1 in the manual). You can assign specific conditions (e.g., overcurrent, undervoltage, harmonic threshold) to each group and configure independent thresholds, delays, and recovery values.
The standard RS485 port supports Modbus-RTU. The optional Ethernet module supports Modbus-TCP and FTP (for SD card file access).
Yes, by ordering the APM521/Log version with the MicroSD card module. The meter can log electrical parameters at configurable intervals (default 1 minute) directly to the SD card, which can later be retrieved via FTP (with Ethernet module) or by physically removing the card.
The default password is 0001. This can be changed in the “System Settings” menu. If you forget the password, please contact our technical support for assistance.
Summary
The APM521 multifunctional network meter offers a comprehensive solution for power monitoring and management. Its high-precision measurement (0.2S), in-depth power quality analysis (up to 63rd harmonics), and modular expandability make it suitable for a wide range of applications, from industrial plants to commercial buildings and data centers. By consolidating multiple functions into a single device, it reduces installation complexity, saves panel space, and provides a unified data source for energy management systems. With flexible communication options including Modbus-RTU and Modbus-TCP, the APM521 integrates seamlessly into modern digital power distribution networks.
