942-A4N-2D-1E1-S136 HONEYWELL

942-A4N-2D-1E1-S136 HONEYWELL Termination Unit

Brand：HONEYWELL Model number：942-A4N-2D-1E1-S136

Country of origin: United States Product weight：0.4kg

HS code：8517623990

Product Details：

Product Dimensions：

A HONEYWELL Termination Unit (often referred to as a T-Unit or Terminal Unit) is a critical component used in process control systems, particularly in conjunction with Distributed Control Systems (DCS) like Honeywell's Experion PKS.

The primary function of a T-Unit is to provide a standardized, robust, and easily maintainable interface between the field wiring (from sensors, transmitters, valves, etc.) and the DCS Input/Output (I/O) modules. This separation of field wiring from the delicate I/O electronics enhances system reliability and simplifies maintenance.

Key Parameters (General)

Channel Density: Typically supports 8, 16, or 32 I/O channels per unit.
I/O Signal Types: Designed to handle standard industrial signals, including:

Analog Input (AI): $4-20\text{ mA}$ , $1-5\text{ V}$ .
Analog Output (AO): $4-20\text{ mA}$ .
Digital Input (DI): $24\text{ V DC}$ , $120\text{ V AC/DC}$ .
Digital Output (DO): Relay or Solid-State Switch outputs.
RTD/Thermocouple (TC) Inputs: Specific models are required for direct temperature sensor connections.

Connection Method: Screw terminals or push-in terminals for field wiring. Specific connectors (e.g., ribbon cable or proprietary connectors) for connection to the DCS I/O module.
Mounting: Often designed for DIN rail mounting in control cabinets.
Environmental Ratings: Must meet standards for industrial environments, including temperature range (e.g., $0\text{°C}$ to $60\text{°C}$ or wider) and humidity.

Product Advantages

The use of HONEYWELL T-Units offers significant benefits in industrial automation projects:

Simplified Maintenance and Troubleshooting: The T-Unit acts as a fixed wiring point. If an I/O module fails, it can be replaced without disconnecting or re-terminating any field wires. This is known as hot-swappability or bumpless replacement.
Increased System Reliability: By isolating the sensitive I/O electronics from field wiring stresses (like accidental pulls or vibration), the T-Unit protects the core control system.
Standardized Installation: They provide a clean, organized, and standardized way to manage hundreds or thousands of field wires, greatly reducing installation time and errors during commissioning.
Integrated Features: Many models include integrated features like:

Cold Junction Compensation (CJC): For accurate thermocouple measurements.
Fuses or Isolation: For channel-by-channel protection.
Diagnostics LEDs: For quick status checks of channel activity or fuse integrity.

Cost-Effective Cabling: They enable the use of pre-fabricated system cables to connect the T-Unit to the I/O module, replacing bulky and complex bundles of individual wires.

Important Considerations (Precautions)

To ensure proper installation and long-term performance, several factors must be strictly observed:

I/O Signal Matching: Always ensure the T-Unit model is precisely matched to the specific Honeywell I/O module and the field signal type (e.g., using a thermocouple T-Unit for a TC module, and an Analog Input T-Unit for a $4-20\text{ mA}$ module). Misalignment can lead to non-functionality or damage.
Proper Grounding and Shielding: Correct grounding of shields and connection of earth grounds are essential for signal integrity, especially for low-level signals like thermocouples and high-speed communications. Refer to the Honeywell system installation standards.
Torque Specifications: When terminating field wires, use the specified torque setting for the screw terminals to prevent loose connections (which cause intermittent faults) or over-tightening (which can damage the terminal block).
Power and Fuse Ratings: If the T-Unit has integrated fuses or requires external power for relay contacts, ensure the ratings are correct and the power source is reliable.

Product Applications

HONEYWELL Termination Units are essential in any industry utilizing large-scale process automation:

Oil & Gas (Upstream, Midstream, Downstream): Used for connecting field instrumentation like pressure, flow, and temperature transmitters, as well as control valves and pump motor controls.
Chemical and Petrochemical Processing: Integration point for safety-critical instruments and extensive regulatory control loops.
Power Generation: Connecting turbine controls, boiler systems, and balance-of-plant instrumentation.
Pulp and Paper: Handling numerous analog and digital inputs from level sensors, motors, and consistency transmitters.
Pharmaceutical and Biotech: Used in validation-intensive environments for reliable connection of sensors in reactors and clean utilities.

51196653-200 HONEYWELL

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