YOKOGAWA AMM42 high-density Analog Input/Output Module
The Yokogawa AMM42 is a high-density Analog Input/Output Module utilized primarily in the CENTUM XL and older CENTUM CS Distributed Control Systems.
It belongs to a generation of modular I/O that specialized in providing a mix of analog signals in a single hardware footprint to optimize cabinet space.
1. Introduction
The AMM42 is designed to handle multiple analog signals, typically converting field-side currents or voltages into digital values for the DCS processor, and vice versa.
It is known for its versatility in older plant architectures, allowing for the integration of standard 4-20 mA loops or 1-5 V signals.
Due to its age, it is frequently sought after as a spare part for maintaining legacy systems that have not yet fully migrated to the modern FIO (Field network I/O) series.
2. Technical Parameter Table
AMM42
| Feature | Specification |
| Model | AMM42 |
| I/O Type | Analog Input and/or Output (Configurable/Mixed) |
| Number of Channels | 8-Channel or 16-Channel (depending on sub-variant) |
| Signal Range | 4 to 20 mA DC / 1 to 5 V DC |
| Input Impedance | 250 $\Omega$ (for current input) / 1 M$\Omega$ (for voltage input) |
| Accuracy | $\pm$ 0.1% of Full Scale |
| A/D & D/A Resolution | 12-bit or 16-bit (depending on revision) |
| Isolation | Input-to-system isolation (Transformer/Optical) |
| Power Consumption | Approx. 3.0 W to 5.0 W |
| Mounting | Card-cage type (Legacy CENTUM racks) |
3. Product Advantages and Features
Space Efficiency: By combining multiple analog paths on a single card, the AMM42 reduced the number of slots required in the I/O nest.
Galvanic Isolation: Protects the sensitive internal DCS logic from field-side surges and ground loops, enhancing system stability.
Robust Construction: Designed for the 15-20 year lifecycles typical of industrial automation, featuring high-quality capacitors and solid-state components.
Backward Compatibility: Seamlessly integrates with the control bus of legacy Field Control Stations (FCS), requiring minimal software configuration.
Proven Track Record: Extensively used in the 1990s and 2000s across the global oil and gas industry, proving its reliability in mission-critical environments.
4. Application Cases
Refinery Control Loops: Monitoring temperature and pressure transmitters and sending control signals to I/P converters for valve positioning.
Legacy Power Plant Monitoring: Interfacing with older analog sensors in boiler and turbine control systems.
Maintenance & Repair (MRO): Used as a direct replacement part for failed modules in aging facilities where a full system upgrade is not yet budgeted.
Water & Wastewater: Controlling pump speeds via variable frequency drives (VFD) through its analog output channels.
5. Related Models & Same Series
The AMM42 is part of a family of “M-series” modules used in legacy Yokogawa nests.
Other Models in the Same Series
AMM12C: A dedicated analog input module for various signal types.
AMM22: A multi-channel analog input module with specific filtering.
AMM32: Primarily focused on analog output signals.
AMM52: Specialized for thermocouple or RTD (temperature) inputs.
Modern Successors (CENTUM VP)
For users looking to modernize, these are the current equivalents in the FIO lineup:
AAI141 / AAI143: 16-channel Analog Input modules.
AAI543: 16-channel Analog Output module.
AAI841: Analog I/O module (Mixed inputs/outputs).
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