IMASI23 ABB Bailey INFI90 Analog Input Slave Module

ABB Bailey IMASI23 is a high-performance analog input module designed for industrial automation control systems and widely used in ABB's Infi 90 and Symphony series distributed control systems. With its high performance, multi-function and high reliability, this module has become an indispensable signal acquisition device in the field of industrial automation.

The ASI module consists of a single printed circuit board that occupies one slot in a module mounting unit (MMU). Two captive latches on the module front panel secure it to the module mounting unit.

The ASI module has three card edge connectors for external signals and power: P1, P2 and P3. P1 connects to the supply voltages. P2 connects the module to the I/O expander bus, over which it communicates with the controller. Connector P3 carries the inputs from the termination cable plugged into the termination unit (TU). The terminal blocks for field wiring are on the termination unit.

A single dipswitch on the module sets its address or selects onboard tests. Jumpers configure the type of analog input signals.

The ASI module is an intelligent module with an onboard microcontroller and memory. It interfaces to a controller over the I/O expander bus. An onboard microcontroller allows the ASI module to perform the input channel processing. This allows the controller to do other tasks. Input processing tasks include error compensation, adjustments, and conversion to engineering units.

Each channel provides underrange, overrange, and open input detection. Onboard circuitry detects either open field wires or a disconnected termination unit cable. Open input detection is provided for millivolt, thermocouple, RTD, 1 to 5 VDC, and 4 to 20 milliampere input types and can detect any combination of open input wires.

Figure 2-1 shows a block diagram of the IMASI23 module.

Each input channel has an A/D converter (delta-sigma type). Isolation is done by DC/DC converters (one per channel) and optocouplers on the digital serial line of the A/D converter. Each channel accepts voltage and resistance inputs. Resistance measurements are made by digitizing the voltage drop created across the input resistance source. A precision constant current source supplies the current used to measure the input.

The ASI module measures the cold junction RTDs on the termination unit of the analog input module. This results in an accurate reading of the ambient temperature at the field wire termination area. This value can be used by the ASI mo connections made by terminating the field wires (thermocouple wires) onto the terminal blocks of the termination unit.dule to compensate for voltages generated from the bimetal

The block address of the cold junction reference used by thermocouple inputs on the ASI module is contained in FC 215, specification S3.

Each analog input module configured for a thermocouple input requires a cold junction reference. Each analog input module can only have one reference which can be used by up to 16 thermocouple inputs. The exception to this is when one of the inputs is used as a remote cold junction reference.

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