NI SCXI-1324

Description

Product Description

The NI SCXI-1324 is a specialized, high-density terminal block designed for use with National Instruments’ SCXI-1125 Isolated Analog Input Module. This terminal block serves as the critical wiring interface that connects field sensors, particularly thermocouples (TCs) or millivolt-level signals, to the high-performance signal conditioning system. The NI SCXI-1324 is not a simple pass-through block; it integrates components essential for accurate thermocouple measurement, including built-in cold-junction compensation (CJC) sensors and connections for precision voltage references. For comprehensive technical specifications, wiring diagrams, and configuration guides, the essential resource is the official National Instruments product page for the NI SCXI-1324. Using the correct SCXI-1324 terminal block is fundamental to achieving the high accuracy and channel-to-channel isolation provided by the SCXI-1125 module. Its design is specifically optimized for multi-channel temperature measurement applications in demanding test and measurement environments.

Product Parameters

• Manufacturer / Brand: National Instruments (NI).
• Series: SCXI (Signal Conditioning Platform).
• Model: SCXI-1324 – Terminal Block for SCXI-1125.
• Function: High-Density, Isolated Thermocouple / Analog Input Terminal Block.
• Compatibility: Designed exclusively for use with the NI SCXI-1125 32-Channel Isolated Analog Input Module.
• Channels: Provides screw terminal connections for 32 differential input channels.
• Integrated Cold-Junction Compensation (CJC): Contains onboard CJC sensors to measure the temperature at the terminal block, which is critical for accurate thermocouple readings.
• Reference Connections: Includes terminals for connecting external precision voltage references (if required for specific measurement modes of the SCXI-1125).
• Shielding: Provides terminals for signal ground and shield connections to manage noise.
• Wiring: Removable screw terminal blocks for all 32 channels.
• Form Factor: Plugs directly into the front connector of the SCXI-1125 module.
• Passive/Active Features: While primarily a wiring interface, it contains passive components and active CJC sensors essential for the measurement function.

Advantages and Features

• Optimized for Thermocouple Measurements: The integrated CJC sensors provide accurate cold-junction temperature measurement directly at the point of connection, eliminating errors from temperature gradients.
• High-Density Channel Access: Provides convenient, screw-terminal access to all 32 isolated channels of the SCXI-1125 module in a compact form factor, maximizing channel count per rack slot.
• Maintains System Isolation: The design preserves the channel-to-channel and channel-to-system isolation provided by the SCXI-1125 module, which is crucial for safety and noise rejection in industrial environments.
• Professional and Reliable Interface: Converts the module’s connector into a robust, industry-standard terminal block, ensuring secure connections and simplified maintenance.
• Simplified System Calibration: Having the CJC sensor integrated into the terminal block simplifies system calibration and improves overall measurement accuracy for thermocouple-based systems.

Application Cases in Industry

• Engine and Powertrain Testing: The NI SCXI-1324 terminal block connects dozens of thermocouples measuring exhaust manifold, cylinder head, and coolant temperatures on an engine dyno test stand to the SCXI-1125 module.
• Aerothermal Testing: Used in wind tunnels or environmental chambers to interface hundreds of thermocouples on aircraft components or models with the data acquisition system for thermal mapping.
• Industrial Process Monitoring: Connects multiple thermocouples from reactors, kilns, or ovens in chemical and materials processing plants to a centralized condition monitoring system.
• Energy Research: Facilitates the connection of numerous temperature sensors in experimental setups for solar thermal, battery, or fuel cell testing.
• HVAC System Testing: Used in laboratory setups to monitor temperatures across complex heating, ventilation, and air conditioning system prototypes.

Comparison with Competing Products

Competing products are high-density thermocouple terminal blocks from other data acquisition vendors, such as Keysight/Agilent 34901A (with CJC) or Measurement Computing offerings. The NI SCXI-1324 differentiates itself through its deep, exclusive integration with the NI SCXI-1125 module. Compared to a generic thermocouple terminal block with separate CJC modules, the SCXI-1324 provides a fully integrated, calibrated, and plug-and-play solution that is automatically recognized and configured by NI-DAQmx software. Its primary advantage is the guarantee of performance and accuracy when used within the NI ecosystem, simplifying engineering and validation time.

Selection Suggestions and Precautions

• Selection Suggestions:
  1. Select the NI SCXI-1324 specifically and exclusively when using the NI SCXI-1125 Isolated Analog Input Module for thermocouple or other low-voltage differential measurements.
  2. For non-thermocouple applications with the SCXI-1125, verify if a simpler terminal block (like the SCXI-1320) might be sufficient, though the SCXI-1324 will still function.
  3. Plan for adequate space and cooling in the SCXI chassis, as a fully loaded system with multiple modules and terminal blocks can generate significant heat.
• Precautions:
  1. CJC Sensor Placement: The terminal block’s CJC sensors measure the block’s temperature. Ensure the SCXI-1324 is installed in a location with stable, uniform ambient temperature and good airflow to avoid thermal gradients across the block.
  2. Correct Thermocouple Wire: Use the correct thermocouple type (J, K, T, E, etc.) and corresponding extension wire all the way to the terminal block. Do not use copper wire for the final run, as this will create an unintended junction.
  3. Secure Connections: Ensure all screw terminals are tightened to the proper specification. Loose connections on low-millivolt signals are a primary source of noise and measurement error.
  4. Shielding and Grounding: Connect the shield drain wires of shielded thermocouple cables to the designated shield terminals on the SCXI-1324. Implement a single-point grounding scheme as recommended in the system design guide.
  5. Handling and Calibration: Handle the terminal block carefully. While the CJC is integrated, the overall system (SCXI-1125 + SCXI-1324) should be periodically verified or calibrated against known standards to ensure long-term measurement accuracy. Source from authorized NI distributors to ensure authenticity.

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