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Invensys 3721
Invensys 3721
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Analog Input Modules

3721

Spare Part Number

PN3721

Product Information:

The Triconex 3721 module employs an industry-leading Triple Module Redundancy (TMR) fault-tolerant architecture, integrating three fully isolated independent signal processing sub-channels. When analog signals from field sensors are input asynchronously, each of the three sub-channels independently performs high-speed acquisition, digital conversion, and isolation processing, sending the data to the main processor via the system backplane bus.

The Triconex 3721's main processor uses a smart voting algorithm (median value in TMR mode) for a "two-out-of-three" logical vote. This hardware-level fault-tolerance mechanism ensures that even if any two channels experience hardware failure or signal anomalies, the system can still output accurate and safe data without interruption, thus preventing false triggering or fail-safe shutdown.

In terms of electrical specifications, the Triconex 3721 provides 32 two-wire DC-coupled differential input channels (marked in yellow on the front panel), supporting voltage signal ranges of 0 to 5 VDC or -5 to +5 VDC. This module features an external 250Ω shunt resistor, ensuring perfect compatibility with standard 4-20mA industrial current signals.

Product image is representative; revision or series may vary. Contact us to request a specific version.
  • One-year warranty
  • Global shipping
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Technical specifications for

3721

0 TECHNICAL PARAMETERS
  • Manufacturer:
    Invensys
  • Product Category:
    ESD System
  • Spare Part Number:
    3721
  • Estimated shipping dimensions:
    2.1x40.8x40cm
  • Weight:
    2.02 kg
  • Tariff Code:
    8537101190
  • Country of origin:
    USA
  • Place of shipment:
    Xiamen, Fujian, China
  • Voltage:
    0 to 5 VDC or -5 to +5 VDC1, + 6%
  • No. of Input Points:
    32 differential, DC-coupled
  • Resolution:
    12 bits or 14 bits programmable
  • Accuracy:
    < 0.15% of FSR from 0° to 60° C
  • Input Resistance (load):
    10 MΩ (DC), min.
  • Power-Off Resistance:
    140 kΩ (DC), typical
  • Common Mode Rejection:
    -85 dB (DC - 100 Hz)
  • Common Mode Range:
    -12V to +12V peak
  • Leg-to-Leg Isolation:
    420 kΩ, typical
  • Input Overrange Prot:
    150 VDC/115 VAC continuous
  • Series:
    Triconex
  • Stock Availability:
    10
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Alternative Names

372I 3700/3700A 3700 3700A 3701 3703E 3704E 3720 372O 370I 37O1 37OI

Information

Overview Manuals TMR System Critical Applications

Features:

  • HART Interface Modules
  • 0 to 5 or –5 to +5 VDC Differential, DC Coupled TMR ype
  • Current Range by 0-20 mA with 250 Ω shunt resistor
Analog Input (AI) Modules 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.

Analog Input Modules require 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.

The 3721 Invensys Triconex Analog Input Modules may still be available for purchase and support from Moore Automated Company beyond End-Of-Life (EOL) by the manufacturer (OEM).
Invensys Triconex 3721 Analog Input Modules manual(Datasheets), Link Important Notice: Other accessories, manuals, cables, calibration data, software, etc. are not included with this equipment unless listed in the above stock item description. All prices are shown in USD.
This module contains three fully isolated internal input channels. Each branch asynchronously reads field signals, converts them into digital values, and transmits them through the backplane. The main processor then applies an intermediate value selection algorithm to ensure 100% data integrity without interrupting processing.
Emergency Shutdown (ESD) System: Continuously monitors the output of pressure, flow, and level transmitters to execute safe shutdown procedures when process parameters exceed safety limits.

Turbine Control Platform: Connects critical speed, vibration, and temperature telemetry sensors to prevent catastrophic failures caused by equipment overspeed.
 
High Integrity Pressure Protection System (HIPPS): Performs ultra-fast, multi-channel processing to trigger isolation valves before extreme pressure peaks threaten piping or the reactor pressure vessel containment.

Technical notes

The Triconex 3721 is a highly available 32-channel DC-coupled differential analog input module designed for Safety Instrumented Systems (SIS), such as Emergency Stop (ESD) and Fire & Gas (F&G) systems. Based on a Triple Module Redundancy (TMR) architecture compliant with IEC 61508 SIL 3, the module features three independent input paths and employs an advanced median selection algorithm to eliminate single-path failures or spike interference. It supports voltage inputs from 0 to 5 VDC or -5 to +5 VDC (0-20 mA current can be obtained via an external 250Ω shunt resistor), provides programmable 12-bit or 14-bit resolution, and has a data update cycle of only 10 milliseconds. Furthermore, it features comprehensive built-in self-diagnostics, continuous overvoltage protection, and hot-swappability, ensuring uninterrupted and accurate signal acquisition in harsh, critical industrial environments such as the petrochemical and power industries.
PRODUCT & ORDER FAQS

Questions buyers ask about 3721

  • What is the primary functional scope of the 3721 within the Triconex safety instrumented system architecture?

    The 3721 module functions as a critical input/output interface within the Triconex architecture, designed to facilitate deterministic and fail-safe data acquisition and control signal transmission, ensuring uncompromised safety integrity level (SIL) performance in safety-critical process automation environments.
  • In what manner does the 3721 module integrate with higher-level Triconex controllers and system software?

    The 3721 communicates through a robust, time-deterministic backplane bus protocol, ensuring seamless data exchange with Triconex controllers and configuration tools, thereby enabling synchronous safety logic execution and real-time status monitoring.
  • What environmental and operational parameters does the 3721 module tolerate during continuous operation?

    Designed for industrial-grade robustness, the 3721 operates reliably within a wide ambient temperature range, withstands electromagnetic interference (EMI), and conforms to rigorous shock and vibration standards, ensuring consistent performance under challenging plant conditions.
  • What advanced diagnostics and status reporting features are embedded within the 3721?

    The 3721 continuously monitors its internal circuitry and I/O channels, providing granular fault indication such as short-circuit, open-circuit, and signal integrity deviations, thus enabling proactive identification of degradation before functional impact.
  • What best practices are recommended for installation and commissioning of the 3721 to maximize performance and reliability?

    Optimal performance of the 3721 necessitates adherence to manufacturer guidelines including precise wiring protocols, electromagnetic shielding, environmental conditioning, and thorough pre-commissioning testing using certified validation tools to ensure compliance with safety lifecycle requirements.
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Moore Disclaimer: Moore Automated's sales automation equipment and related solutions are intended for industrial automation and business operational efficiency improvement purposes only. Product information, technical parameters, and application cases are for reference only and do not constitute an absolute guarantee of performance for any specific industry, scenario, or final application. Actual equipment performance may vary depending on factors such as the usage environment, system integration method, and maintenance conditions. Users should confirm compatibility and safety based on professional technical assessments. Moore Automated assumes no liability for any direct or indirect losses caused by improper use, modification, or failure to operate according to specifications, to the extent permitted by law.

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