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Yokogawa ALU4*D Modular I/O System

The Yokogawa AAI141, also cataloged as the ALU4D* Analog Input Module, operates as a dedicated hardware component for 4-20 mA DC signal acquisition within Yokogawa CENTUM VP and CENTUM CS 3000 distributed control systems.

Hardware Specifications

Parameter	Specification
Model Brand	Yokogawa ALU4*D Series
Origin	Japan
Weight	0.2 kg
Dimensions	Standard DIN-rail mount modular width
Operating Temp	0 to 60 degC
Power Consumption	310 mA @ 5 VDC, 450 mA @ 24 VDC
Number of Input Channels	16, non-isolated
Input Signal Range	4 to 20 mA DC, 1 to 5 V DC, -10 to 10 V DC
Allowable Common Mode Voltage	±1 V or less
Input Resistance (Power ON)	400 Ohm @ 20 mA, 1000 Ohm @ 4 mA, 1 MOhm or larger
Input Resistance (Power OFF)	500 kOhm or larger, 340 kOhm or larger, 660 kOhm or larger
Accuracy	±16 uA, ±4 mV, ±20 mV
Data Update Period	10 ms
Step Response Time	100 ms
Transmitter Power Supply	14.8 V or higher @ 20 mA, 26.4 V or less @ 0 mA
Output Current Limit	27 mA

4-20 mA HART Loop Protocol Handling

Channel-level configuration pins define 2-wire or 4-wire transmitter excitation sourcing. The module supplies a regulated 24 VDC loop power rail to active field devices. The input circuitry tolerates a maximum common mode voltage of ±1 V DC. Transmitter supply voltage regulation maintains output above 14.8 V DC under full 20 mA load conditions. The input resistance profile scales inversely with current magnitude, presenting 400 Ohm at 20 mA and rising to 1000 Ohm at 4 mA. This characteristic requires verification against field transmitter load drive capability specifications.

Frequently Asked Questions

Q: Does the ALU4*D support hot-swapping while the CENTUM VP node is operational?

A: Yes, the module supports online replacement. The system backplane maintains communication integrity during the exchange procedure. Verify that the replacement unit matches the existing I/O assignment configuration prior to insertion.

Q: What is the impact of non-isolated channel design on wiring practices?

A: All 16 input channels share a common reference potential. Field wiring must ensure that external sensor grounds do not introduce ground loops exceeding the ±1 V common mode limit. Use isolated barrier devices if field device grounding conflicts occur.

Q: How does temperature drift affect calibration intervals?

A: Accuracy drift is specified at ±16 uA per 10 degC. For applications requiring sustained high precision, perform field calibration checks when ambient temperature variations exceed 30 degC from the initial calibration environment.

Field Installation Guidelines

Mount the module onto the dedicated Yokogawa baseplate assembly. Use the pressure clamp terminal blocks for field wiring termination. Ensure that the shield drain wire connects directly to the designated earth ground point on the baseplate to maintain signal integrity. Torque terminal screws to the manufacturer-specified value to prevent thermal expansion loosening. Verify that the KS cable or MIL connector routing avoids parallel runs with high-voltage power conductors to minimize electromagnetic interference pickup.

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