Overview
The IMASI23 is a Harmony rack I/O module integrated into ABB’s Symphony Enterprise
Management and Control System, designed for high-precision analog signal acquisition in industrial
automation scenarios (e.g., process control, temperature/pressure monitoring in oil & gas, chemical,
and power sectors). It features 16 independent analog input channels, each equipped with a
dedicated 24-bit analog-to-digital (A/D) converter—delivering exceptional resolution for accurate
signal conversion of thermocouples, millivolt signals, RTDs (Resistance Temperature Detectors), and
high-level analog signals (voltage/current).
A key advantage of the IMASI23 is its flexibility: each channel can be independently configured to
match the desired input type (e.g., Type K thermocouple, 4–20 mA current, 100Ω RTD), allowing
mixed-signal integration on a single module. It also supports seamless replacement of legacy ABB
modules (IMASI03/IMASI13) with only minor modifications—specifically, updating Specification S11
in Function Code (FC) 216 to reflect 24-bit resolution and verifying power supply compatibility (due to
slight differences in power consumption).
Physically, the module occupies one slot in a standard ABB Module Mounting Unit (MMU) and
interfaces with the Symphony system via the I/O Expander Bus. It incorporates robust safety and
diagnostic features, including electrostatic discharge (ESD) protection, open-input detection, and
automatic calibration to compensate for component drift—ensuring reliable operation in harsh
industrial environments (0–70°C ambient temperature, 5–95% non-condensing humidity).
Core Functionality
2.1 High-Precision Analog Signal Acquisition & Conversion
The IMASI23’s primary function is to interface 16 channels of analog field signals to Symphony system controllers (e.g., Harmony area controllers, rack controllers) for process monitoring and control. Key capabilities include:
Multi-Signal Compatibility: Supports a wide range of input types, including:
Thermocouples: Type B, E, J, K, L, N (14/28 AWG), R, S, T, U, and Chinese Type E/S.
RTDs: 3-wire configurations (10Ω, 100Ω U.S./European, 120Ω nickel, 53Ω Chinese copper).
Millivolt signals: -100 to +100 mV.
High-level signals: 4–20 mA current, ±10 VDC/0–10 VDC/0–5 VDC/1–5 VDC voltage.
24-Bit A/D Resolution: Each channel has a dedicated delta-sigma A/D converter, ensuring high accuracy (0.02% full-scale for current, 0.04% for high-level voltage) and minimal noise interference.
Cold Junction Compensation: Critical for thermocouple inputs—uses built-in RTDs on the NTAI06 Termination Unit to measure ambient temperature at field wiring terminations, correcting for voltage offsets caused by bimetal junctions.
2.2 Automatic Calibration & Error Correction
To maintain long-term accuracy without manual intervention, the IMASI23 includes:
Factory Calibration: Offset, gain, and nonlinearity errors are pre-calibrated at the factory, with correction factors stored in nonvolatile memory (NVRAM) for real-time application during signal processing.
Automatic Recalibration: Periodically adjusts A/D converters using an internal precision reference to compensate for component aging and temperature drift—transparent to normal operation.
User Gain/Offset Tuning: Allows fine adjustments via FC 217 to correct for field-specific signal deviations (e.g., a 0.1 VDC offset in a 0–10 VDC input), with settings retained in NVRAM even during power loss.
2.3 Communication & Integration with Symphony System
The IMASI23 acts as a bridge between field devices and the Symphony system, enabling seamless data flow and configuration:
I/O Expander Bus Interface: Communicates with controllers via a high-speed synchronous parallel bus (I/O Expander Bus) on the MMU backplane. A dual-port RAM (DPRAM) ensures simultaneous data access by the module’s microcontroller and the system controller, enabling real-time signal transmission.
Online Configuration: Supports dynamic updates to channel settings (via FC 215/216) without powering down the system. When configurations change, the module holds the last valid signal value temporarily (up to 4 seconds per channel) to avoid process disruptions.
Legacy Compatibility: Directly replaces IMASI03/IMASI13 modules with minimal changes—only requiring FC 216 adjustments (resolution) and power supply verification (IMASI23 draws 500 mA @ 5 VDC, vs. 300 mA for IMASI03).
2.4 Diagnostics & Safety Features
The module includes built-in safeguards to ensure operational integrity and simplify troubleshooting:
Open-Input Detection: Identifies open field wires or disconnected termination cables for all input types (except ±10 VDC/0–10 VDC/0–5 VDC), flagging bad quality for affected channels.
Power-Up & Runtime Diagnostics: Performs self-tests (ROM/NVRAM checks, A/D reference verification, watchdog timer tests) on power-up and during operation. Fatal errors (e.g., A/D failure) trigger a solid red LED, while communication loss causes a blinking green LED.
ESD & Electrical Protection: Classified as an Electrostatic Sensitive Device (ESD)—requires handling with ABB’s Field Static Kit (P/N 1948385A1) to prevent damage. Also includes channel-to-channel isolation (1.4 kV RMS for 1 minute) and common-mode rejection (-80 dB @ 50/60 Hz) to mitigate interference.
2.5 Termination & Wiring Flexibility
The IMASI23 uses the NTAI06 Termination Unit (connected via NKAS01/NKAS11 cables) for field wiring, with jumper configurations to match input types (e.g., system-powered vs. externally powered 4–20 mA). The termination unit also includes fuses (2 A @ +24 VDC) to protect the system from short circuits, and its enclosure maintains consistent temperature for accurate cold junction compensation.
ABB Bailey INFI 90 Series: System Structure & Key Components
The ABB Bailey INFI 90 series is a modular distributed process control system (DCS) tailored for
industrial automation and safety-critical scenarios, featuring a hierarchical architecture that connects
field equipment, slave modules, master controllers, and operator interfaces. At its core, the system
relies on master-slave communication to enable process monitoring and control: the Multi-Function
Processor (MFP: IMMFP01/02) and Network 90 Multi-Function Controllers serve as central master
units, while the IMASI02 (Analog Slave Input Module) acts as a dedicated slave component that
inputs 15 channels of analog signals from field devices (e.g., sensors, Bailey smart transmitters) to the
master controllers. Critical supporting components include termination devices (NTAI05 Termination
Unit, NIAI04 Termination Module) that configure and route field signals to the IMASI02 via specialized
cables (NKTU01, NKTM01), and the Slave Expander Bus (a backplane-mounted parallel bus in the
Module Mounting Unit/MMU) that enables real-time data exchange between the IMASI02 and MFP.
Operator interfaces like the Operator Interface Station (OIS), Configuration and Tuning Terminal (CTT),
and Smart Transmitter Terminal (STT) further integrate with the system—allowing users to configure
the MFP (via FC 132/133), send commands to smart transmitters through the IMASI02, and monitor
process status, while the Controlway and INFI-NET/Plant Loop provide redundant, plant-wide
communication for seamless scalability.
