1. Product Overview

Product Name: 8 Channel Differential Voltage/Current Analog Input Module
Model: SM_AI_108i
Series: SUNIX ioSCADA SM Series
Article Number: SM_AI_108i
Manufacturer: Sunix Group

The SM_AI_108i is an industrial-grade analog input module designed for high-precision data acquisition in distributed control systems (DCS), programmable logic controllers (PLC), and supervisory control and data acquisition (SCADA) environments. It is part of the SUNIX ioSCADA SM series, a family of modular I/O devices supporting the Modbus RTU and ASCII protocols over RS-485 communication. The module provides eight differential analog input channels capable of measuring both current and voltage signals with high accuracy and isolation, making it suitable for demanding industrial automation and monitoring applications.

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2. Key Features

- Eight Differential Analog Input Channels: Supports independent measurement of voltage and current signals across eight isolated channels.
- Multi-Range Input Capability: Configurable for ±20 mA, 4–20 mA, ±10 V, ±5 V, and 1–5 V input ranges.
- High Resolution and Accuracy: 16-bit A/D conversion with ±0.05% accuracy at 25°C, ensuring precise signal acquisition.
- Channel-to-Channel Isolation: Each input channel is electrically isolated to prevent cross-interference and enhance signal integrity.
- Automatic Noise Filtering: Integrated 50/60 Hz auto noise filter with 60 dB normal mode and 88 dB common mode rejection.
- Industrial-Grade Protection: Overvoltage protection up to 60 VAC and overcurrent protection up to 300 mA.
- Hardware Watchdog: Ensures continuous operation and system recovery in case of communication or hardware failure.
- Wide Operating Temperature Range: Designed for harsh environments, operating reliably from -30°C to +75°C.
- DIN-Rail Mountable: Compact industrial enclosure (132 × 125 × 47.5 mm) for easy installation in control panels.
- Standard Modbus Communication: Compatible with Modbus RTU and ASCII protocols over RS-485 (3-wire).
- User-Friendly Configuration: DIP switch settings for baud rate, address, and protocol selection; no software required for basic setup.
- LED Status Indicators: Visual feedback for power, communication, and I/O activity.
- High Noise Immunity: Compliant with IEC61000-4-4 EFT Level 3 and IEC61000-4-2 ESD Level 3 standards.
- Network Scalability: Supports up to 63 modules on a single RS-485 bus without a repeater, with a maximum network distance of 4000 feet.

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3. Technical Specifications

- Input Channels: 8 differential
- Input Signal Ranges: ±20 mA, 4–20 mA, ±10 V, ±5 V, 1–5 V
- Resolution: 16-bit (1 part in 32,000)
- Accuracy: ±0.05% of input range at 25°C
- Temperature Coefficient: Better than ±0.005% of input span per °C or ±1.0 µV/°C
- Input Conversion Rate: 140 ms per channel
- Input Resistance:
- Current input: 250 Ω
- Voltage input: 380 kΩ
- Input Filter Bandwidth: -3 dB at 1.5 Hz (typical)
- Noise Rejection:
- Normal mode: 60 dB @ 60 Hz
- Common mode: 88 dB @ 60 Hz
- Overvoltage Protection: 60 VAC (voltage inputs)
- Overcurrent Protection: 300 mA (current inputs)
- Isolation Voltage: 3000 Vrms (RS-485, field-to-logic, and channel-to-channel)
- Power Supply: 10–30 VDC
- Power Consumption: Typical 0.1094 A @ 24 VDC
- Operating Temperature: -30°C to +75°C
- Storage Temperature: -45°C to +85°C
- Relative Humidity: 5–90%, non-condensing
- Dimensions: 132 × 125 × 47.5 mm
- Mounting: DIN-rail
- Weight: Approx. 0.5 kg

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4. Functionality

The SM_AI_108i module converts analog voltage or current signals into digital data for transmission over an RS-485 Modbus network. Each channel can be independently configured for voltage or current input, allowing flexible integration with various sensors and transducers. The module’s 16-bit A/D converter ensures high-resolution signal acquisition, while built-in filtering and isolation maintain measurement stability in electrically noisy environments.

Typical Applications:
- Industrial process monitoring (temperature, pressure, flow, level)
- Energy management systems
- Power plant instrumentation
- Steel manufacturing and petrochemical process control
- Environmental monitoring (air, water, and pollution systems)
- Building automation and HVAC control
- Laboratory and test automation

Compatibility:
- Fully compatible with Modbus RTU/ASCII master devices such as PLCs, DCS, PACs, and SCADA software (e.g., LabView, Wonderware, Citect, Intellution).

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5. Components & Accessories

Included Items:
- SM_AI_108i module
- DIN-rail mounting kit
- Installation CD with ioCFG configuration software
- Quick installation guide

Optional Accessories:
- RS-232/RS-485 isolation converter
- RS-485 repeater (for networks exceeding 1200 m)
- Shielded twisted-pair communication cables (16–24 AWG)

Connectors:
- Removable terminal blocks for power, communication, and I/O connections
- RS-485 interface: Data+, Data–, COM

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6. Installation & Setup

Requirements:
- Power supply: 10–30 VDC (industrial-grade, IEC61000-4-4 compliant)
- Host system: PC, PLC, or SCADA master with RS-485 interface
- Communication: Shielded twisted-pair cable, maximum 4000 ft without repeater

Mounting Options:
- DIN-rail (horizontal or vertical orientation)
- Panel mounting with optional accessories

Configuration:
- DIP switch settings for baud rate (1200–115200 bps), Modbus address (1–63), and protocol (RTU/ASCII)
- Default settings: 115.2 kbps, address 1, RTU mode
- Reset to factory defaults via DIP switch (INIT function)

LED Indicators:
- PWR: Power status
- RX/TX: Communication activity
- IO_ACC: I/O access status
- Rt_ON: RS-485 termination resistor status

Software Setup:
- ioCFG configuration utility (Windows-based) for advanced parameter setup, monitoring, and diagnostics
- Supports online/offline configuration, auto-scan, and EEPROM parameter storage

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7. Performance & Capabilities

- Conversion Speed: 140 ms per channel
- Resolution: 16-bit (±32,000 counts)
- Accuracy: ±0.05% of full scale
- Noise Rejection: 60 dB (normal mode), 88 dB (common mode)
- Isolation: 3-way (RS-485, field-to-logic, channel-to-channel)
- Network Capacity: Up to 63 modules per RS-485 segment
- Communication Speed: Up to 115.2 kbps
- Network Distance: 4000 ft (without repeater)
- Reliability: Dual watchdog (hardware and communication) ensures continuous operation
- Environmental Robustness: Designed for high EMI/RFI immunity and extended temperature operation

Limitations:
- Maximum of 48 Modbus registers per message (RTU mode)
- Voltage input protection limited to 60 VAC
- Current input protection limited to 300 mA

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8. Standards & Compliance

- Communication Protocols: Modbus RTU and ASCII (RS-485, 3-wire)
- Isolation Voltage: 3000 Vrms (RS-485 and field-to-logic)
- EMC Compliance:
- IEC61000-4-4 EFT Level 3 (power and signal lines)
- IEC61000-4-2 ESD Level 3 (8 kV air, 4 kV contact)
- IEC61000-4-5 Surge Immunity (0.5 kV)
- CE Certified: Meets European EMC and safety standards
- Environmental Ratings: Industrial-grade, suitable for harsh environments
- Network Standards: EIA RS-485 compliant

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9. Additional Information

Warranty:
Sunix Group provides a limited warranty covering manufacturing defects for two years from the date of delivery or one year after installation (whichever occurs first). The warranty excludes damage caused by improper installation, misuse, or operation outside specified conditions.

Support & Service Policy:
- Free repair, testing, and adjustment during the warranty period (shipping costs borne by the customer).
- Post-warranty service available at approximately 25% of product price.
- RMA (Return Material Authorization) required for all returns.
- Technical support available through Sunix Tech Forum and authorized distributors.

Maintenance:
- Periodic inspection of wiring and terminal connections recommended.
- Ensure proper grounding (PE) and shielding for noise immunity.
- Use only industrial-grade power supplies and communication cables.

Firmware & Updates:
- Firmware version and module ID accessible via Modbus function code 17 (Report Slave ID).
- Configuration parameters stored in nonvolatile EEPROM.
- Factory reset available via DIP switch (INIT).

Power Consumption:
Typical 0.1094 A @ 24 VDC (2.63 W), maximum 0.2149 A @ 10 VDC, minimum 0.0902 A @ 30 VDC.

Physical Construction:
- Industrial-grade plastic enclosure with pull-out terminal blocks for easy maintenance.
- Slide-in labeling panel for channel identification.
- Integrated RS-485 termination resistor selectable via DIP switch.

Safety Notes:
- Not designed for human life-support or rescue applications.
- Ensure compliance with local electrical codes and grounding practices.

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Summary

The Sunix SM_AI_108i is a robust, high-precision analog input module engineered for industrial automation and SCADA systems. With eight isolated differential channels, 16-bit resolution, and flexible voltage/current input ranges, it delivers reliable and accurate signal acquisition in harsh environments. Its Modbus RTU/ASCII compatibility, hardware watchdog, and 3-way isolation make it ideal for distributed control networks requiring stability, scalability, and ease of integration. The module’s compact DIN-rail design, wide operating temperature range, and compliance with IEC and CE standards ensure dependable performance across diverse industrial applications.