ICS Triplex T3401 DC Digital Input Modules

T3401 Modules

ICS Triplex Digital DC input modules provide input detection for 16 fields input switches.

There are three types of modules available for Interface to inputs fed from a 24, 48, or 120 VDC field power supplies

The tripled I / O security bus of each module.

The interface ensures that no module failure can affect Regent system operation or other I / O modules in the system.

Extensive fault detection and criticism announcement redundant circuits help prevent controllers from receiving erroneous data of a faulty input module.

Three DC digital input modules can be connected in parallel to obtain fault-tolerant input sensing.

In this triple module configuration, a failed module can be removed and replaced without interrupting the input signals.

T3401 Features

· Sixteen input circuits configured as two isolated groups of eight circuits each.

· Fault-tolerant operation when connected in parallel with redundant modules of the same type.

· Hot-replaceable.

· Automatic self-testing of triplicated I/O Safetybus circuits and many simplex logic circuits.

· Individual front panel indicators on each module show active and fault status and logic-side input on/off status.

· 2500 volt minimum electrical isolation between field and logic circuits.

· TÜV certified, Risk Class 5.

T3401 Operation

A block diagram of a typical DC digital input module is shown in Figure 1.

Optical isolation between field wiring and the modules’ logic circuitry provides field-to-logic isolation — protecting the modules’ logic circuits from field signal over-voltages, transients, and other electrical disturbances.

It also provides a safety barrier between the primary field voltages and user-accessible circuits.

Figure 1. Block Diagram of the DC Digital Input Module.

When the field switch is closed, the input to the module is on.

When the field switch opens, the input to the module turns off.

Data from the logic side of the optical isolators are bused to the I/O bus interface logic.

The processor modules send triplicated read data requests to the input module over the I/O Safetybus.

The processors’ addressing data and data read requests are voted by the module (preventing I/O Safetybus failures upstream from the module from affecting its ability to be read).

The voted result is then passed to the I/O bus interface logic.

After receiving the voted data read request, the I/O bus interface logic sends its input data to the module’s three bus drivers.

Each of the three bus drivers is independently powered and controlled by the I/O transceiver modules— preventing failures in a single driver from propagating to the other two busses.

The bus drivers transmit the data across the backplane I/O Safetybus to the I/O transceivers which, in turn, transmit the data to the processors.

Testing and Diagnostics

Each module’s voter circuits are periodically tested by the processor modules. Discrepant data are sent through one of three legs of the I/O Safetybus to determine whether the module’s voter is able to outvote the incorrect data.

A failure to return the correct majority-voted result to the processors produces an I/O module error indication at the processor modules and a module fault indication at the I/O module.

Each type of module has a unique identification code that is read by the controller.

This code lets the controller know which type of module is installed in each I/O chassis slot and how to address that module and its points specifically.

If a module is removed or is replaced with a module of a different type, the processor modules will indicate I/O module errors.

Loopback logic tests periodically write data to the module and then read it back to determine whether the module’s I/O bus interface logic is functioning correctly.

Front Panel Indicators

Figure 2 shows the physical features of the DC digital input modules.

The front panel of each module contains active and fault status indicators and field signal status indicators for each circuit.

Active and Fault Status Indicators

These green and red LEDs indicate the overall health of the module.

During normal operation, the green ACTIVE indicator flashes at the controller's scan rate.

If a module fault is detected the red FAULT indicator turns on and the green indicator turns off.

Field Status Indicators

Input status indicators are located on the logic-side (after the signal conditioning and isolation).

The field status indicators are lit when current is flowing through the input.

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