NI SCXI-1327

Description

Product Description

The NI SCXI-1327 is a high-density, 68-pin screw-terminal block designed specifically for use with National Instruments SCXI (Signal Conditioning eXtensions for Instrumentation) modules, particularly those within the SCXI-110X series and other compatible analog input modules. This terminal block is a critical interface component that bridges the gap between field wiring and the sensitive signal conditioning electronics of the SCXI system. Its primary function is to provide a robust, organized, and easily accessible point for connecting up to 32 analog input signals (or other I/O) to the corresponding SCXI module via a standard 68-pin ribbon cable. The NI SCXI-1327 translates the high-density connector on the module into individual, clearly labeled screw terminals, simplifying the installation, maintenance, and troubleshooting of complex data acquisition (DAQ) systems. Implementing this terminal block is essential for building reliable and maintainable test, measurement, and control racks, especially in applications requiring the connection of numerous sensors or signals.

Technical Parameters and Features

• Device Type: 68-pin Screw-Terminal Block for SCXI modules.
• Compatibility: Designed for specific SCXI modules, most notably the SCXI-1102B/C 32-channel multiplexer amplifier modules, and other modules using the 68-pin front-signal connector.
• Terminal Count: Provides 68 screw terminals, corresponding to the pins on the connector. This typically breaks down into terminals for:
  • 32 Analog Input Channels (HI and LO for each).
  • Analog Ground (AGND) and Digital Ground (DGND) references.
  • +5V Sense and other utility lines.
• Terminal Type: Screw-clamp terminals suitable for solid or stranded wire, typically accommodating wire gauges in the range of AWG 22-30.
• Connector: A 68-pin female connector on the rear that mates directly with the male connector on the front of the compatible SCXI module via a supplied ribbon cable.
• Marking: Clearly labeled terminal designations (e.g., CH0H, CH0L, AGND) silk-screened next to each terminal for accurate wiring according to the module’s pinout.
• Mounting: Designed to mount on a standard 19-inch rack panel or other flat surface. It is not a DIN-rail mount component.
• Accessory Role: It is a passive accessory; it does not perform signal conditioning, amplification, or isolation itself. Its quality and proper use are vital for signal integrity.

Advantages and Key Features

• Simplified High-Density Wiring: The NI SCXI-1327 is the essential solution for connecting a large number of field wires to a compact SCXI module. It eliminates the need for fragile, direct cable soldering to the module’s connector.
• Professional and Organized Installation: By providing a sturdy, labeled terminal strip, it enables a neat and professional wiring job. This organization is crucial for system reliability, troubleshooting, and future modifications.
• Protected Module Interface: It acts as a sacrificial and replaceable interface. Wear and tear from frequent wire changes occur on the terminal block, not on the expensive SCXI module’s built-in connector, extending the life of the core hardware.
• Clear Signal Identification: The printed channel labels directly adjacent to each screw terminal prevent wiring errors, which is critical in systems with dozens of analog channels where a mistake can be time-consuming to diagnose.
• System Integration: As a genuine NI accessory, the SCXI-1327 is mechanically and electrically guaranteed to be compatible with its designated modules, ensuring reliable connections and signal paths.

Application Case Studies in Various Fields

• Automotive Test Bench: Used in an engine dynamometer test cell, where an SCXI-1102 module with an SCXI-1327 terminal block connects 32 thermocouples measuring exhaust manifold, coolant, and oil temperatures to a PXI-based DAQ system.
• Aerospace Structural Test: In a wing fatigue test, multiple strain gauge bridges are wired into several NI SCXI-1327 blocks, which feed conditioned signals from SCXI-1520 strain gauge modules to the data acquisition controller for real-time stress monitoring.
• Industrial Machinery Monitoring: For condition monitoring of a large pump or compressor, vibration sensors (accelerometers) and proximity probes are wired to the terminal block, which interfaces with an SCXI module for anti-aliasing filtering and amplification before digitization.
• University Research Lab: In a physics or engineering lab, the terminal block is used to neatly organize connections from various experimental sensors (pressure, temperature, voltage) to a versatile SCXI-based measurement system.

Comparison with Competing Products

Compared to using generic terminal blocks or custom-built interface panels, the NI SCXI-1327 is a purpose-engineered accessory:

1. Guaranteed Compatibility vs. Generic Blocks: A generic 68-pin terminal block may have the same pin count, but the SCXI-1327 is specifically keyed and pinned to match NI’s connector and includes the correct labeling for the associated module’s pinout. This eliminates guesswork and potential damage from misalignment.
2. System-Centric Design: It is part of the integrated SCXI system philosophy, which includes shielded ribbon cables of specified length. Competing solutions often involve assembling separate cables, connectors, and blocks, which can introduce noise and reliability issues.
3. Signal Integrity Focus: While passive, its design considers the needs of analog signal integrity, providing terminals for guards and senses that generic blocks do not. Using an incorrect block can degrade measurement accuracy in sensitive applications.

Selection Advice and Important Notes

• Verify Module Compatibility: This is the most critical step. The NI SCXI-1327 is not universal. Confirm in the SCXI module’s datasheet or user manual that the SCXI-1327 is listed as the recommended or compatible terminal block. Using it with an incompatible module will not work.
• Use the Correct Ribbon Cable: The terminal block is typically sold with or requires a specific shielded 68-pin ribbon cable (e.g., SHC68-68-EPM or equivalent) of an appropriate length to connect to the module. Do not substitute with unshielded or incorrect cables.
• Follow Proper Wiring Practices: Use the specified wire gauge. For analog signals, use twisted-pair wires and connect shields appropriately (often to the AGND terminal as per the system design). Keep wire runs from sensors to the terminal block as short as possible.
• Implement Good Grounding: Properly connect the AGND and DGND terminals of the SCXI-1327 to the system’s central star ground point as defined in the SCXI system installation guide to minimize ground loops.
• Plan for Accessibility: Mount the terminal block in a location that allows easy access for wiring and maintenance, considering the length of the ribbon cable connecting it to the SCXI module in the rack.

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