Tricon System Introduction

The Tricon is a state-of-the art controller that provides fault tolerance by means of Triple-Modular Redundant (TMR) architecture. TMR integrates three isolated, parallel control systems and extensive diagnostics in one control system. The system uses two-out-ofthree voting to provide high-integrity, error-free, uninterrupted process operation with no single point of failure.

The Tricon controller uses three identical channels. Each channel independently executes the control program in parallel with the other two channels. Specialized hardware/software voting mechanisms qualify and verify all digital inputs and outputs from the field, while analog inputs are subject to a mid-value selection process. Because each channel is isolated from the others, no single-point failure in any channel can pass to another. If a hardware failure does occur on one channel, the other channels override it. Meanwhile the faulting module can easily be removed and replaced while thecontroller is online without interrupting the process. Setting up control programs is simplified with the triplicated Tricon system, because it operates as a single control system from the user’s point of view. The user terminates sensors and actuators at a single wiring terminal andprograms the Tricon with one set of control program logic.

The Tricon controller manages the rest! Extensive diagnostics on each channel, module, and functional circuit immediately detect and report operational faults by means of indicators or alarms.

Termination Configuration Options  

Terminations are available in various factory configurations:

• Non-commoned Terminations can accommodate individual power supplies for each point.

• Commoned Terminations can support one power supply which is shared by multiple points. Points can be commoned in groups of 8 and groups of 16.

• Analog signals can be read as 3-wire transmitter inputs, voltage inputs or current inputs.

• Thermocouple terminations provide cold-junction temperature sensors and are available for either upscale or downscale burnout detection. For the model 3706A, upscale or downscale burnout detection depends on which termination panel is installed. For model 3708E, upscale or downscale burnout detection is configured with TriStation. 

The “Termination Options” table (on the next two pages) shows the available termination choices for each I/O module and gives the correct model number for each choice.

Analog Input Modules

An analog input (AI) module includes three independent input channels. Each input channel receives variable voltage signals from each point, converts them to digital values, and transmits the values to the three main processor modules on demand. In TMR mode, one value is then selected using a midvalue selection algorithm to ensure correct data for every scan.

Sensing of each input point is performed in a manner that prevents a single failure on one channel from  affecting another channel. Each analog input module sustains complete, ongoing diagnostics for each channel. Failure of any diagnostic on any channel activates the Fault indicator for the module, which in turn activates the chassis alarm signal. The module’s Fault indicator merely reports a channel fault, not a module failure—the module can operate properly with as many as two faulty channels. Analog input modules support hotspare capability which allows online replacement of a faulty module

The analog input module requires a separate external termination panel (ETP) with a cable interface to the Tricon backplane. Each module is mechanically keyed for proper installation in a Tricon chassis.