PLCs, Power Supplies & Others

The Yokogawa AAI135 is an 8-channel analog input module purpose-built for CENTUM CS 3000 and CENTUM VP distributed control systems. Each channel provides complete galvanic isolation from both system logic and adjacent channels. This module additionally supports HART communication for intelligent device integration.

Key Technical Specifications

Complete Channel-to-Channel Isolation

The AAI135 distinguishes itself through true per-channel galvanic isolation. You therefore connect field devices with different ground potentials without circulating currents. Each input withstands 500 V AC between itself and both system ground and adjacent channels. This isolation eliminates ground loops entirely.

Integrated Transmitter Power Supply

You do not require external power supplies for two-wire transmitters. The AAI135 provides regulated loop power from its internal 24 V DC input. Each channel delivers 15.0 volts at 20 milliamps continuously. Consequently, you simplify cabinet wiring and reduce component count.

HART Communication Pass-Through Capability

This module passes HART digital signals superimposed on the 4–20 mA analog current. You therefore configure and monitor smart transmitters without additional hardware. The AAI135 preserves both analog measurement integrity and digital communication simultaneously. Asset management software accesses device diagnostics through the same module.

Ten-Millisecond Update for Critical Loops

All eight channels update simultaneously every 10 milliseconds. This refresh rate supports fast-responding pressure and flow control loops. You achieve true simultaneous sampling across all connected transmitters. The AAI135 therefore suits reactor monitoring and compressor surge control.

Precision ±16 Microamp Accuracy

Yokogawa guarantees accuracy within ±16 microamps across the full 4–20 mA span. This precision represents 0.1 percent of span or better. Temperature drift adds only ±16 microamps per 10 °C change. Your critical measurements remain reliable despite ambient temperature swings.

Input Resistance Characteristics

The AAI135 presents 290 to 450 ohms input impedance when powered. This resistance varies slightly with instantaneous current value. During power-off conditions, input impedance rises to 500 kilohms. You therefore safely connect or disconnect transmitters while the module is de-energized.

Power Consumption and System Integration

This module consumes 360 milliamps from the 5 V logic supply. It additionally draws 450 milliamps from the 24 V field power source. You install the AAI135 directly into ESB or ER bus node units. Pressure clamp terminals and MIL connectors accommodate various wiring preferences.

Hazardous Area Considerations

The AAI135 does not meet RoHS material restrictions by design. You must install appropriate isolation barriers when using this module in explosive atmospheres. The module itself suits general-purpose and non-hazardous locations. This distinction ensures safe operation within appropriate application boundaries.

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