ICS Triplex T9851 | TMR Analog Output Module
ICS Triplex T9851 | TMR Analog Output Module - Image 2
ICS Triplex T9851 | TMR Analog Output Module - Image 3
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ICS Triplex T9851 | TMR Analog Output Module

  • Brand:​ ICS Triplex
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    Model:​ T9851
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    Product Type:​ TMR Analog Output Module
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    Series:​ Trusted System
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    Core Function:​ Provides 8 channels of triple redundant 4-20mA analog output for safety instrumented systems.
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    Key Specs:​ 8 channels, 4-20mA output, TMR architecture, HART protocol support.
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Part number: ICS Triplex T9851
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Description

T9851: Product Overview
The ICS Triplex T9851 is a triple modular redundant (TMR) analog output module designed for high-integrity safety instrumented systems within the Trusted platform. This module functions as the critical interface between the safety controller and final control elements, providing fault-tolerant command signals to control valves, variable frequency drives, and other analog-controlled field devices. The module implements a robust architecture where three independent output channels generate each analog signal, with voting logic that ensures correct operation even during internal component failures.
Installed in a Trusted system chassis, the module provides 8 channels of 4-20mA analog outputs with integrated support for the HART digital communication protocol. Each output channel incorporates three completely independent digital-to-analog converters, current drivers, and isolation barriers. The voting logic compares the output of all three channels continuously, using a median-select algorithm to verify that the correct current is being delivered to the field device. This design ensures that a single component failure in any part of the output circuitry does not cause an incorrect control action that could compromise process safety.
As part of the Trusted safety platform, this analog output module supports the high availability and safety integrity levels required in critical process safety applications. The design includes comprehensive diagnostics that monitor output channel health, detect field wiring faults, and verify that the correct current is being delivered to field devices. The module performs continuous self-tests of the output circuitry, including DAC linearity checks and current loop verification. This diagnostic coverage, combined with the hardware redundancy, provides the necessary features to achieve Safety Integrity Level (SIL) 3 certification according to IEC 61508 standards.
T9851: Technical Specifications
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    Model Number:​ T9851
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    Manufacturer:​ ICS Triplex
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    Product Type:​ TMR Analog Output Module
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    Number of Channels:​ 8 channels
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    Output Type:​ 4-20mA analog current loop
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    Output Range:​ 0-24mA programmable
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    Resolution:​ 16-bit
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    Accuracy:​ ±0.05% of span
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    Update Rate:​ 100ms per channel
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    Load Compliance:​ 0-600 ohms at 20mA
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    HART Support:​ Yes, digital communication superimposed on analog signal
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    Output Ramp Rate:​ Configurable, 1-60 seconds
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    Isolation:​ 1500V AC channel-to-channel and channel-to-system
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    Voting Logic:​ Median select with continuous comparison
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    Diagnostics:​ Open circuit detection, short circuit detection, output verification
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    Safety Integrity:​ SIL 3 capable per IEC 61508
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    Operating Temperature:​ -40°C to +70°C
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    Connection:​ Removable terminal blocks
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    Status Indicators:​ Per-channel health and status LEDs
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    Power Supply:​ 24V DC nominal (18-32V DC range)

Core Features & Customer Value
Triple Modular Redundant Output Generation: The TMR design provides three independent signal generation paths for each analog output, ensuring that a single component failure cannot cause an incorrect control signal to be sent to field devices. The median-select voting continuously compares all three output currents and automatically disregards any channel that deviates significantly from the others. This architecture is particularly critical for analog outputs, as they directly control final elements that regulate process conditions. The redundancy ensures that control valves and other critical equipment receive the correct command signal even during internal hardware failures.
HART Protocol Integration for Advanced Diagnostics: The module supports bidirectional HART communication, allowing it to send secondary variables and diagnostic information to smart field devices while maintaining the primary 4-20mA control signal. This capability enables advanced device configuration, calibration verification, and predictive maintenance strategies. The module can also receive diagnostic information from HART-enabled field devices, providing comprehensive insight into the health of the final control element and its associated wiring.
Configurable Output Characteristics: The module supports programmable output ranges and ramp rates, allowing engineers to tailor the output behavior to specific application requirements. Slow ramp rates can be configured for applications requiring gradual process changes, while fast response times are available for critical control applications. The programmable output range allows the module to interface with various field devices that may require different signal ranges, providing flexibility in system design and integration.
Typical Applications
In safety-related control applications, the module provides command signals to control valves in emergency depressurizing systems and emergency ventilation control dampers. The TMR architecture ensures that these critical control elements receive the correct command signal even during component failures, maintaining process safety while avoiding spurious operations.
For turbine control systems, the module interfaces with fuel control valves and inlet guide vanes, providing precise analog control signals for speed and load regulation. The high resolution and accuracy enable precise control of turbine parameters, while the fault-tolerant design ensures continuous operation during component failures.
In fire and gas systems, the module can control variable speed drives for emergency ventilation fans, allowing for modulated response to gas concentrations rather than simple on/off control. The HART capability enables communication with smart positioners on dampers and other final control elements, providing additional diagnostic information and control flexibility.

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