Overview
The AIM-D200-CAI DC insulation monitor is an advanced device designed for unearthed DC systems (IT systems) in electric vehicle charging applications. It continuously monitors the insulation resistance of both positive and negative poles to earth, while also providing precise current measurement via external shunt. Based on the unbalanced bridge principle, it overcomes the limitation of balanced bridges that fail to detect faults when both poles are simultaneously grounded. When insulation resistance falls below preset thresholds, the device issues pre-alarm or alarm signals via LED indicators. Designed for DC 100-1000V systems, it is ideal for EV charging stations, energy storage systems, substation DC panels, UPS systems, and photovoltaic DC networks. The monitor features communication-triggered measurement mode, ensuring minimal impact on system insulation, and offers compact DIN rail mounting with plug-in terminals.
Highlight
Integrated Current Measurement
- External shunt connection
- 0.5% accuracy, range customizable
- Monitors system current in real time
High Precision Insulation
- 1kΩ-10MΩ, accuracy ≤5% (10-500kΩ)
- Response time 500ms or 1000ms
- Unbalanced bridge design
Flexible Trigger Modes
- Communication trigger (default)
- Periodic trigger with adjustable delay
- Ideal for on-demand EV charging checks
Compact DIN Rail Design
- Standard 35mm rail mounting
- Low power ≤6W, plug-in terminals
- LED status indication (run, comm, fault)
Function
| Insulation Monitoring | Continuously measures insulation resistance of positive and negative poles to earth. Range: 1kΩ～10MΩ. Pre-alarm and alarm thresholds can be set independently. |
| Voltage Monitoring | Real-time measurement of system voltage (pole-to-pole) and pole-to-earth voltages. Range: DC 100～1000V. Reverse polarity indication via fault register. |
| Current Monitoring | Measures DC system current via external shunt (user-selectable rating). Accuracy class 0.5. |
| LED Indication | Panel LEDs indicate running, communication, and fault status (pre-alarm flashing, alarm steady). |
| Dual Trigger Modes | Communication trigger (default): reading any measurement register initiates one insulation measurement. Periodic trigger: automatic measurement with adjustable delay (5-500s). |
| Unbalanced Bridge Principle | Effectively detects insulation faults even when both poles are simultaneously grounded. |
| DIN Rail Mounting | Standard 35mm DIN rail mounting for easy installation in control cabinets. |
| Plug–in Terminals | Plug-in terminal blocks simplify wiring and maintenance. |
| Special Communication Parameter Configuration | Unique fixed-frame command allows reading/writing of address and baud rate without opening the device. |
Specification
| Parameter | Value |
| Auxiliary Power | DC 12～36V |
| Max. Power Consumption | ≤6 W |
| Voltage Measurement Range | DC 100～1000V |
| Voltage Accuracy | Class 2.0 |
| Current Measurement | External shunt (user-selectable rating) |
| Current Accuracy | Class 0.5 |
| Insulation Resistance Range | 1 kΩ ～ 10 MΩ |
| Pre-alarm / Alarm Setting Range | 10 kΩ ～ 10 MΩ |
| Insulation Accuracy | 1～10 kΩ: ±1 kΩ 10～500 kΩ: ≤5% |
| Permissible System Leakage Capacitance | ≤5 μF |
| Insulation Monitoring Time | 500 ms / 1000 ms per cycle (selectable) |
| Alarm Indication | LEDs (run, comm, fault: pre-alarm flashing, alarm steady) |
| Communication Interface | RS485, Modbus-RTU protocol |
| Communication Address | 1～63 (software configurable, default 1) |
| Baud Rate | 4800, 9600, 19200, 38400 bps (software configurable, default 9600) |
| Insulation Monitoring Method | Communication trigger (default) or periodic trigger |
| Periodic Trigger Delay | 5～500 s adjustable (when in periodic mode) |
| Insulation Capacitance Time | 0～60000 ms adjustable (for systems >5μF) |
| Mounting | 35mm DIN rail |
| Protection Degree | IP30 |
| Operating Temperature | –20 °C ～ +60 °C |
| Storage Temperature | –25 °C ～ +75 °C |
| Relative Humidity | <95% (non-condensing) |
| Altitude | <2000 m |
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FAQ
The AIM-D200-CAI uniquely integrates current measurement capability via external shunt, allowing it to monitor system current in addition to insulation resistance and voltage. This makes it ideal for EV charging applications where current monitoring is required.
The shunt connects to terminals 4 (shunt positive) and 5 (shunt negative) on the bottom terminal block. The shunt rating should be selected based on your system’s maximum current. The measured value is available in register 26H with a scaling factor of 0.01A.
Insulation accuracy is ±1kΩ for the 1-10kΩ range, and ≤5% for the 10-500kΩ range. For very low insulation values, the absolute accuracy ensures reliable fault detection.
Communication parameters can be configured via Modbus registers (01H for address, 02H for baud rate). Additionally, a special fixed-frame command (“ACREL-AIMD200” + parameters) allows reading/writing of address and baud rate without needing to know the current settings.
No, the trigger mode is selectable via register 40H (0x01 for periodic, 0x10 for communication trigger). Communication trigger is default and recommended for EV charging applications where on-demand measurement is preferred.
Summary
The AIM-D200-CAI DC insulation monitor is a comprehensive solution for EV charging stations, uniquely combining insulation monitoring, voltage measurement, and current measurement in a single DIN rail device. With high-precision insulation detection based on the unbalanced bridge principle, flexible trigger modes, and easy communication configuration, it ensures safe and reliable charging operations. Its compact design, low power consumption, and plug-in terminals make it easy to integrate into new or existing charging infrastructure, energy storage systems, and industrial DC networks requiring both insulation and current monitoring.
