The Tricon controller incorporates integral online diagnostics. Probable failure modes are anticipated and made detectable by specialized circuitry. Fault-monitoring circuitry in each module helps fulfill this requirement. The circuitry includes but is not limited to I/O loopback, deadman timers, loss-of-power sensors, and so on. This aspect of the system design enables the Tricon controller to reconfigure itself and perform limited self-repair according to the health of each module and channel.

Each Tricon controller module can activate the system integrity alarm. The alarm consists of a normally closed or normally opened (NC or NO) relay contact on each Power Module. Any failure condition, including loss or brownout of system power, activates the alarm to summon plant maintenance personnel.

The front panel of each module provides LED (light-emitting-diode) indicators that show the status of the module or the external systems to which it is connected. Pass, Fault, and Active are common indicators. Other indicators are specific to each module.

Maintenance consists of replacing plug-in modules. A lighted Fault indicator shows that the module has detected a fault and must be replaced. The control circuitry for the indicators is isolated from each of the three channels and is redundant.

All internal diagnostic and alarm status data is available for remote logging and report generation. This reporting is done through a local or remote TriStation PC, or through a host computer. For more information, see the TriStation 1131 Developer’s Guide for the version of TriStation being used.

Analog Input Modules

For Analog Input Modules, each of the three channels asynchronously measures the input signals and places the results into a table of values. Each of the three input tables is passed to its associated Main Processor using the I/O bus. The input table in each Main Processor is transferred to its neighbors across the TriBus. The middle value is selected by each Main Processor and the input table in each Main Processor is corrected accordingly. In TMR mode, the mid-value data is used by the control program; in duplex mode, the average is used.

Each Analog Input Module is automatically calibrated using multiple reference voltages read through the multiplexer. These voltages determine the gain and bias required to adjust readings of the analog-to-digital converter.

Analog Input Modules and termination panels are available to support a wide variety of analog inputs, in both isolated and non-isolated versions: 0 to 5 VDC, -5 to +5 VDC, 0 to 10 VDC, 4 to 20 mA, thermocouples (types K, J, T and E), and resistive thermal devices (RTD).

Analog Output Modules

An Analog Output Module receives three tables of output values, one for each channel from the corresponding Main Processor. Each channel has its own digital-to-analog converter (DAC). One of the three channels is selected to drive the analog outputs. The output is continuously checked for correctness by loopback inputs on each point which are read by all three microprocessors. If a fault occurs in the driving channel, that channel is declared faulty, and a new channel is selected to drive the field device. The designation of driving channel is rotated among the channels so that all three channels are periodically tested.

Each Analog Output Module is guaranteed to remain in calibration for the life of the controller; periodic manual calibration is not required.

Digital Input Modules

Every Digital Input Module houses the circuitry for three identical channels (A, B, and C). Although the channels reside on the same module, they are completely isolated from each other and operate independently, which means a fault on one channel cannot pass to another. In addition, each channel contains an 8-bit microprocessor called the I/O communication processor which handles communication with its corresponding Main Processor.

Each of the three input channels asynchronously measures the input signals from each point on the input module, determines the respective states of the input signals, and places the values into input tables A, B, and C respectively. Each input table is regularly interrogated over the I/O bus by the I/O communication processor located on the corresponding Main Processor. For example, Main Processor A interrogates Input Table A over I/O Bus A.

There are two basic types of Digital Input Modules: TMR and Single.

TMR Digital Input Modules

On TMR Digital Input Modules, all critical signal paths are 100 percent triplicated to guarantee safety and maximum availability. Each channel conditions signals independently and provides isolation between the field and the Tricon controller. The Model 3504E high-density module is an exception—it has no channel-to-channel isolation.

Models 3502E, 3503E, and 3505E include a self-test feature which verifies the ability of the Tricon controller to detect transitions from a normally energized circuit to the Off state. Because most safety systems use a de-energize-to-trip setting, the ability to detect the Off state is an important feature. To test for stuck-On inputs, a switch within the input circuitry is closed to allow a zero input (Off) to be read by the optical isolation circuitry. The last data reading is frozen in the I/O Processor while the test is running.

Single Digital Input Modules

On Single Digital Input Modules, only those portions of the signal path which are required to ensure safe operation are triplicated. Single modules are optimized for those safety-critical applications where low cost is more important than maximum availability. Special self-test circuitry detects all stuck-On and stuck-Off fault conditions within the non-triplicated signal conditioners in less than half a second. This is a mandatory feature of a fail-safe system, which must detect all faults in a timely manner, and upon detection of an input fault, force the measured input value to the safe state. Because the Tricon controller is optimized for deenergize-to-trip applications, detection of a fault in the input circuitry forces to Off (the deenergized state) the value reported to the Main Processors by each channel.

Digital Output Modules

Every Digital Output Module houses the circuitry for three identical, isolated channels. Each channel includes an I/O microprocessor which receives its output table from the I/O Processor on its corresponding Main Processor. All of the Digital Output Modules, except the dual DC modules, use a patented quadruplicated output circuitry, referred to as Quad Voter, which votes on the individual output signals just before they are applied to the load. This voter circuitry is based on parallel-series paths which pass power if the drivers for Channels A and B, or Channels B and C, or Channels A and C command them to close—in other words, 2-out-of-3 drivers voted On. Dual Digital Output Modules provide a single series path, with the 2-out-of3 voting process applied individually to each switch. The quadruplicated output circuitry provides multiple redundancy for all critical signal paths, guaranteeing safety and maximum availability.

OVD (Output Voter Diagnostics)

Every Digital Output Module executes a specific type of Output Voter Diagnostics (OVD) for every point. This safety feature allows unrestricted operation under a variety of multiple-fault scenarios. In general, during OVD execution the commanded state of each point is momentarily reversed on one of the output drivers, one after another. Loopback on the module allows each microprocessor to read the output value for the point to determine whether a latent fault exists within the output circuit. (For devices that cannot tolerate a signal transition of any length, OVD on both AC and DC voltage Digital Output Modules can be disabled.)
Same functional module:
TRICONEX   3504E
TRICONEX   3511
TRICONEX   3515
TRICONEX 3601E
TRICONEX 3604E
TRICONEX 3607E
TRICONEX   3623T
TRICONEX   3625
TRICONEX  3625A
TRICONEX   3625C1
TRICONEX   3625
TRICONEX 3636R
TRICONEX   3664
TRICONEX 3700A
TRICONEX 3703E
TRICONEX   3708E
TRICONEX   3708EN
TRICONEX   3721C
TRICONEX 3721
TRICONEX   3805E
TRICONEX   3806E
TRICONEX 3902AX
TRICONEX 4000056-002
TRICONEX 4000066-025
More…