HONEYWELL SAI-1620M

Description

Product Description

The HONEYWELL SAI-1620M is a high-density, 16-channel Analog Input (AI) multiplexer module from the legacy ScantLine I/O family, a foundational system in many Honeywell TDC 2000/3000 and early Experion PKS deployments. This specialized module is designed to efficiently and cost-effectively handle a large number of analog measurement signals, such as those from temperature sensors (RTDs, thermocouples) and millivolt/volt-level transmitters. The primary function of the HONEYWELL SAI-1620M is to sequentially scan, or multiplex, its 16 input channels, converting each analog signal into a digital value for the host controller. By providing this concentrated signal acquisition in a single module slot, the HONEYWELL SAI-1620M plays a crucial role in legacy system architecture, enabling comprehensive process monitoring. For facilities maintaining and supporting older Honeywell DCS installations, the HONEYWELL SAI-1620M remains a vital component for data acquisition, and its continued operation is key to preserving system functionality and valuable historical process data.

Product Parameters

• Product Type: Analog Input Multiplexer Module.
• I/O Type: 16-channel Analog Input (AI).
• Signal Compatibility: Configurable to accept various analog input types, typically including thermocouples (Types J, K, T, E, etc.), RTDs (Pt100, Pt1000), millivolt, and voltage signals. Specific configuration is set via internal jumpers or configuration tables.
• Scanning Method: Uses a multiplexer to sequentially connect each channel to a single, high-precision Analog-to-Digital Converter (ADC).
• Communication: Interfaces with the host process controller (e.g., an HPM or APM) via the legacy ScantLine I/O bus.
• Resolution: High-resolution ADC (e.g., 16-bit) for accurate measurement across the configured input range.
• Isolation: Typically provides channel-to-channel isolation and isolation from the system bus to ensure signal integrity.
• Mounting: Installs into a dedicated slot within a Honeywell ScantLine I/O cabinet or housing.
• Configuration: Channel type, range, and filtering are configured via the control system’s engineering software (e.g., TPS or Experion builder) and/or hardware settings on the module.

Advantages and Features

• High Channel Density: Provides 16 analog input points in a single module, which was a highly efficient design for its era, maximizing I/O count within limited cabinet space.
• Signal Versatility: The ability to configure each channel individually for different sensor types (TC, RTD, voltage) provided significant flexibility for complex plants with diverse instrumentation.
• Proven Reliability: As a core component of the widely installed ScantLine system, the HONEYWELL SAI-1620M has a long, proven track record of reliable operation in harsh industrial environments.
• Legacy System Support: This module is essential for maintaining the operational life of thousands of installed TDC 2000/3000 and early Experion systems worldwide, protecting capital investment.
• Diagnostic Capability: Includes basic module health diagnostics and can report channel-specific faults (e.g., open sensor detection for RTDs), aiding in maintenance.

Application Cases in Application Fields

• Refinery Crude Unit: Multiplexing 16 thermocouple inputs from a crude distillation column’s tray temperatures for fractionation control and monitoring.
• Chemical Batch Reactor: Monitoring multiple RTDs for jacket temperature, internal batch temperature, and condenser outlet temperature in a single SAI-1620M module.
• Power Plant Boiler: Acquiring numerous millivolt signals from draft pressure transmitters and thermocouple signals from superheater and reheater sections.
• Pulp & Paper Digester: Scanning a series of thermocouples along the length of a continuous digester to monitor the cooking temperature profile.

Comparisons with Competing Products

Competing contemporary products from the same era included analog input multiplexers from other DCS vendors like Foxboro (I/A Series) or Bailey (INFI-90). In the modern context, the HONEYWELL SAI-1620M is compared to newer Honeywell I/O (like Universal I/O or C/E Series) and modern PLC analog cards. The key differentiators are architecture and technology. Newer modules offer faster, simultaneous sampling, higher channel-to-channel isolation, more advanced diagnostics, and integration with modern networking. The HONEYWELL SAI-1620M is a slower, multiplexed design from a proprietary, legacy bus architecture. Its primary advantage today is not performance against modern products, but its critical role as a legacy spare part. It ensures continuity for existing systems where a wholesale upgrade is not feasible. For legacy system support, a genuine HONEYWELL SAI-1620M is irreplaceable, whereas for new projects, modern alternatives are vastly superior.

Selection Suggestions and Precautions

1. Legacy System Verification: Confirm that your existing system is a Honeywell TDC 2000/3000 or early Experion PKS with ScantLine I/O. Verify the exact controller model (HPM, APM) and I/O cabinet type to ensure compatibility.
2. Configuration Knowledge: Programming and configuring the HONEYWELL SAI-1620M requires specific knowledge of the legacy control software (e.g., TPS, LCN) and the module’s hardware jumper settings. Access to original documentation or a seasoned system engineer is crucial.
3. Spare Parts Strategy: Given its status as a legacy component, source modules from authorized Honeywell channels or reputable surplus dealers. Verify the module’s condition and configuration match your existing setup. Procuring a spare module for critical loops is highly advised.
4. Signal Type Matching: Double-check that the module is configured for the correct input type (e.g., J-Type TC, Pt100 RTD) for each channel. A mismatch will result in inaccurate readings.
5. Scan Rate Limitation: Understand that the multiplexed design means channels are not sampled simultaneously. This sequential scanning introduces a small time skew between channel readings, which may be important for very fast-acting processes or precise correlation calculations. This is an inherent characteristic of the HONEYWELL SAI-1620M design.

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