YOKOGAWA AMM42

Description

YOKOGAWA AMM42 is a multi-function, multi-input digital mixer or arithmetic station designed for use within the YEWPACK or earlier CENTUM series Distributed Control Systems (DCS) from Yokogawa. This unit, the AMM42, performs complex calculations, signal selection, and auxiliary control functions on multiple analog inputs, providing enhanced control strategies beyond basic PID loops. Detailed information can be found on the product page: YOKOGAWA AMM42. The YOKOGAWA AMM42 was a key component for implementing advanced process calculations and optimizations within vintage Yokogawa control architectures.

Product Description

The YOKOGAWA AMM42 is a specialized computing station housed in a module that installs into a YEWPACK or CENTUM cabinet. It operates as a dedicated analog processing unit, accepting several (typically 4 or more) analog input signals from other field control stations or transmitters. Internally, it is programmed to execute a variety of mathematical and logical functions, such as addition, subtraction, multiplication, division, square root extraction, high/low signal selection, and averaging. The result of these calculations is then output as a standard analog signal (e.g., 4-20 mA) that can be used as a setpoint for another controller, a feedforward signal, or a displayed value. The AMM42 essentially acts as a programmable analog computer within the DCS framework, enabling customized signal conditioning and calculation without burdening the main regulatory controllers.

Product Parameters

• Brand and Manufacturer: YOKOGAWA.
• Series/System: Designed for the YEWPACK or early CENTUM (e.g., CENTUM-XL, CENTUM CS) DCS.
• Product Type: Multi-Input Computing Station, Arithmetic Station, Digital Mixer.
• Number of Inputs: Multiple analog input channels (e.g., 4 or 8 inputs), accepting standard 1-5V DC or 4-20 mA signals.
• Computational Functions: Programmable for a wide range of arithmetic operations (+, -, *, /), square root, high/low selector, middle selector, and averaging.
• Number of Outputs: Typically one or two analog output channels (4-20 mA) for the result of the computation.
• Configuration: Programmed via a dedicated fill-in-the-blanks sheet or earlier engineering tools specific to the YEWPACK/CENTUM system, defining the mathematical relationship between inputs and outputs.
• Communication: Integrated into the system via the YEWPACK/CENTUM proprietary control network (e.g., HF bus).
• Power Supply: Powered from the system’s cabinet power distribution.

Advantages and Features

The primary advantage of the YOKOGAWA AMM42 in its era was its ability to offload complex calculations from the main control processors, improving system efficiency and responsiveness for specialized tasks. It provided a flexible and reliable way to create custom algorithms for feedforward control, ratio control, calorific value calculation, or totalization. Its dedicated hardware design ensured deterministic execution of calculations. A key feature was its relative ease of configuration compared to low-level programming, using predefined function blocks. For its time, the YOKOGAWA AMM42 was a powerful tool for optimizing process control strategies and improving operational efficiency in complex plants like refineries and chemical plants.

Application Cases in Various Fields

• Boiler Efficiency Calculation: Taking inputs of fuel flow, steam flow, and fuel calorific value to compute and output overall boiler efficiency.
• Blending and Ratio Control: Calculating the setpoint for a flow controller based on the ratio of two or more ingredient flows (e.g., in a gasoline blender).
• Flow Compensation: Compensating a differential pressure-based flow signal for changes in process temperature and pressure using multiplication and square root functions.
• Feedforward Control: Calculating a disturbance variable (e.g., feed rate) and outputting a pre-emptive correction signal to a downstream controller to improve response time.
• Signal Selection for Safety: Implementing a high-select or low-select logic among multiple temperature or pressure readings to choose the most critical value for alarm or shutdown logic.

Comparison with Competing Products

In its functional generation, the YOKOGAWA AMM42 competed with similar computing stations from other contemporary DCS vendors like Honeywell (TDC 2000/3000), Foxboro (SPEC 200), and Bailey (Network 90). Each had their own equivalent “multifunction calculator” or “characterizer” module. The competition was at the system level. Compared to modern solutions, the functionality of the AMM42 is now almost universally performed in software within the control processor of a modern DCS or PLC using function blocks. Therefore, the AMM42 is largely seen as a legacy or vintage component, with its primary “competition” being system migration or replacement with a modern platform that offers vastly greater flexibility and integration.

Selection Suggestions and Precautions

1. Legacy System Consideration: The AMM42 is a component for older, possibly obsolete, Yokogawa systems. Selection today is almost exclusively for maintenance, spare parts, or like-for-like replacement in an existing, operational system.
2. Exact Replacement Verification: If used as a spare, the AMM42 model must exactly match the failed unit in terms of hardware revision and software configuration. Systems of this age often have very specific compatibility requirements.
3. Configuration Knowledge: Configuration of the unit requires knowledge of the old system’s engineering methods and access to the original configuration sheets or tools. This expertise is becoming rare.
4. Obsolescence and Support: Be aware that technical support and spare parts for the YOKOGAWA AMM42 may be limited or discontinued. Yokogawa likely recommends migration to a current system (e.g., CENTUM VP) for long-term support.
5. Documentation is Key: Ensure you have the original system manuals, loop diagrams, and configuration details for the specific AMM42 unit in question before attempting any maintenance or replacement.

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