HIMA X-AI3251 Analog Input Module
The HIMA X-AI3251 is a high-density, safety-certified Analog Input (AI) module belonging to the HIMax series of Safety Instrumented Systems (SIS). It is crucial for monitoring continuous process variables, such as pressure, temperature, level, and flow, in applications demanding high reliability and SIL 3 functional safety.
Key Technical Specifications
Module Type
Analog Input (AI)
Measures continuous signals from field transmitters (sensors).
System
HIMax PES
High-availability, fault-tolerant platform for safety applications.
Safety Integrity Level (SIL)
SIL 3
Certified according to IEC 61508, suitable for the most critical safety loops.
Number of Channels
32
Provides 32 channels, typically configurable as single-ended inputs.
Signal Type
4-20 mA / 0-20 mA
Designed primarily to handle standard current signals, which are robust against noise and signal degradation over long cables.
Resolution
High (typically 16-bit or greater)
Ensures precise measurement of the analog signal for accurate safety monitoring.
Channel Type
Non-isolated (per channel)
Channels share a common reference, but the module is typically isolated from the backplane power.
Diagnostic Capabilities
Yes (Built-in)
Features line fault detection (e.g., sensor open circuit, short circuit) and continuous self-testing to ensure data integrity.
System Connection
HIMA System Connector (96-pin)
Connects to the HIMax backplane and Termination Boards (FTAs).
Function and Application
The X-AI3251 is essential for safety functions that depend on the value of a continuous process variable to initiate a trip or safety action. These applications include:
High-High/Low-Low Pressure Protection: Monitoring transmitters to ensure process variables remain within safe operating limits.
Safety Overfill Protection: Monitoring level transmitters in tanks and vessels to prevent hazardous releases.
Turbine Overspeed Protection: Monitoring sensors providing speed signals to prevent catastrophic equipment failure.
Key Advantages of the X-AI3251
High Density & Scalability: With 32 channels, it efficiently manages a large number of analog monitoring points, simplifying system design.
SIL 3 Compliance: The architecture and built-in diagnostics provide the necessary fault tolerance and diagnostic coverage required for SIL 3 safety loops.
Real-Time Diagnostics: Continuous monitoring of the signal path helps ensure that the sensor measurement is valid and accurate, minimizing the risk of a failure on demand (PFD).
Associated Termination Boards
For connecting field wires, the X-AI3251 uses a dedicated Field Termination Assembly (FTA). A common compatible board is:
HiCTB32-HIM-RAC-SP-AI3251: A termination board specifically designed to match the pinout and signal requirements of the X-AI3251 module.
