NI SCXI-1349

Electrical Signal Parameters

• Connector Pin Configuration: 68-pin female rear chassis bus connector, matched to NI E/M series DAQ card 68-pin shielded cable pinout mapping
• Maximum Rated Signal Operating Voltage: 30 V RMS, 42 V peak, 60 V DC maximum signal voltage
• Signal Transmission Type: Supports multiplexed differential analog input signals, digital control bus signals between SCXI chassis and DAQ host card
• Shielding Performance: Full 360° metal EMI/RF shielding enclosure, continuous shielding contact between cable shield layer and adapter metal housing to eliminate shielding discontinuity noise leakage

Environmental & Physical

• Operating Temperature: 0°C ~ 50°C
• Storage Temperature: -20°C ~ 70°C
• Relative Humidity: 10% ~ 90% non-condensing
• Mechanical Form Factor: Standard SCXI single-width plug-in module form factor, installed into the final slot of the last cascaded SCXI chassis

Functional Features

1. Multi-Chassis Cascading Termination Function: Specifically designed as the termination adapter for the final chassis in multi-SCXI cascaded system architectures; paired with SCXI-1346 multi-chassis shielded adapters for front cascaded chassis interconnection, forming a complete shielded multi-chassis signal transmission chain.
2. Full 360° Electromagnetic Shielding Design: The entire adapter housing is constructed from continuous thick metal shielding material; the 68-pin shielded DAQ cable’s outer shielding braid makes full contact with the adapter metal shell, eliminating shielding gaps that allow EMI interference to leak into signal transmission lines and distort analog measurement signals.
3. Standardized DAQ Cable Compatibility: Fully compatible with all NI 68-pin shielded DAQ cables designed for E-series and M-series PCI/PXI DAQ acquisition cards, enabling plug-and-play interconnection between the SCXI chassis backplane multiplexed signal bus and the host computer DAQ hardware.
4. Single-Slot SCXI Chassis Plug-In Installation: Standard single-width SCXI module form factor, simply inserted into the final empty slot of the last cascaded SCXI chassis and locked via front panel thumbscrews, no additional DIN rail or external mounting hardware required.
5. Stable Signal Ground Reference Circuitry: Internal PCB integrates dedicated analog ground and digital ground separation circuits to eliminate analog-digital signal ground crosstalk noise during multiplexed signal transmission from the SCXI chassis to the DAQ host card.

   Working Principle

   In a multi-chassis cascaded SCXI measurement system, front cascaded SCXI chassis units interconnect via SCXI-1346 multi-chassis shielded adapters to transmit the multiplexed analog and digital signal bus sequentially between each chassis backplane. The final chassis in the cascaded chain is fitted with an SCXI-1349 shielded cable adapter installed in its last slot. The multiplexed combined signal bus from all preceding cascaded chassis is transmitted through the chassis backplane bus to the SCXI-1349 adapter’s internal PCB signal separation circuits, which separate analog measurement signals and digital control bus signals while maintaining independent analog/digital grounding paths to suppress signal crosstalk noise. The 68-pin shielded DAQ cable connects the rear 68-pin female connector of SCXI-1349 to the matching port on the PCI/PXI DAQ host card, delivering all multiplexed measurement and control signals to the computer’s DAQ hardware for

   signal conversion, data acquisition and real-time signal analysis. The full surrounding metal shell forms a closed shielding cavity, which absorbs and isolates external electromagnetic radiation, avoiding high-frequency interference signals from mixing into weak analog measurement signals and reducing measurement deviation.

   Material & Structural Characteristics

   1. Shielded Metal Housing: Die-cast aluminum alloy integrated shell, the whole body is fully sealed without splicing gaps, surface conductive oxidation treatment to ensure continuous shielding conduction; internal lining wave-absorbing rubber strips to absorb residual high-frequency stray signals inside the cavity.
   2. Internal Circuit Substrate: Low-noise FR4 glass fiber printed circuit board, double-sided acrylic conformal coating to prevent dust, moisture and slight corrosive gas erosion inside the industrial cabinet; independent analog and digital ground copper foil isolation layout to cut off ground loop crosstalk.
   3. Connector Hardware: Gold-plated 68-pin female signal connector at the rear, thickened copper alloy contact needles with anti-oxidation plating layer, stable low-impedance contact with DAQ shielded cables; gold-plated SCXI backplane bus male connector at the bottom for signal docking with the chassis internal bus.
   4. Locking & Fixing Components: Metal anti-loosening thumbscrews on the front panel, with plastic anti-slip rotating caps; internal circuit boards are fixed by silicone shock-absorbing gaskets to avoid solder joint desoldering caused by cabinet mechanical vibration.
   5. Insulating Auxiliary Parts: High-temperature flame-retardant plastic insulating partitions between analog and digital signal traces on the PCB, effectively isolating high-speed digital switching noise from low-amplitude analog measurement signals.

   Installation Requirements

   1. Chassis Slot Restriction: The SCXI-1349 must be installed in the last empty single-width slot of the terminal SCXI chassis in the cascaded system; it cannot be placed in the middle or front chassis slots, otherwise the multi-chassis signal bus transmission path will be broken.
   2. Cable Matching Rule: Only use NI official 68-pin fully shielded DAQ cables for connection; unshielded, half-shielded or third-party non-matching cables are prohibited, which will destroy the overall EMI shielding effect of the measurement system.
   3. Pre-Power-Off Installation Operation: All insertion, removal and replacement operations of the SCXI-1349 must be completed after cutting off the total power supply of all cascaded SCXI chassis; hot plugging will generate instantaneous high voltage surge and burn the internal signal circuit of the adapter and DAQ host card.
   4. Shield Ground Wiring Standard: The metal ground lug on the bottom of the adapter housing must be connected to the cabinet’s dedicated low-impedance protective earth bar with flat copper grounding strips (width ≥10mm), single-point grounding to avoid multi-point grounding forming ground loops.
   5. Cabinet Environmental Installation Limits: Install the chassis equipped with SCXI-1349 in a fully sealed metal industrial control cabinet with dust filter and ventilation heat dissipation holes; avoid placing the cabinet next to high-power frequency converters, contactors and other strong interference equipment, and ensure the ambient operating temperature is maintained between 0°C and 50°C.
   6. Cable Layout Specification: The 68-pin DAQ shielded cable connected to the rear of the adapter must be routed separately from high-current AC power cables inside the cabinet, and metal shielding partitions must be used for isolation if parallel wiring is unavoidable; the cable shielding layer must be fully clamped to the metal cabinet shell for 360° shielding continuity.

   Application Scenarios

   1. Multi-chassis cascaded large-scale industrial multi-point analog signal acquisition systems, serving as the terminal signal transmission adapter connecting SCXI chassis and PCI/PXI DAQ acquisition cards.
   2. Power equipment comprehensive performance test benches, realizing synchronous transmission of multi-channel voltage, current analog signals and digital control signals from SCXI signal conditioning modules to computer DAQ hardware.
   3. Automotive electronic component automated measurement test systems, completing multi-chassis signal bus convergence and shielded transmission to ensure low-noise collection of weak sensor analog signals.
   4. Aerospace component precision parameter measurement platforms, isolating external high-frequency electromagnetic interference in the test workshop through full metal shielding to guarantee high-precision analog measurement data output.
   5. Laboratory multi-functional integrated DAQ measurement systems, realizing flexible expansion of measurement channels through multi-chassis cascading, with SCXI-1349 as the core terminal interconnection accessory for signal output to host computer acquisition hardware.

   Operation & Usage Precautions

   1. Prohibition of Hot Plugging Warning: Do not insert or pull out the SCXI-1349 adapter or the connected 68-pin DAQ cable when the SCXI chassis and DAQ host card are powered on; instantaneous electrostatic discharge and power surge will permanently damage the internal precision signal circuits of the adapter and DAQ card.
   2. Shielding Integrity Maintenance: Do not drill holes, cut or bend the aluminum alloy shielding housing of the adapter at will; any damage to the shell will form shielding gaps, leading to external EMI interference penetrating into the signal transmission path and causing serious measurement noise and data distortion.
   3. Ambient Humidity Control: If the industrial control cabinet is in a high-humidity working environment with relative humidity higher than 85% for a long time, a cabinet dehumidifier must be installed; excessive humidity will cause condensation on the internal PCB circuit board of the adapter, resulting in signal short-circuit, leakage current and unstable measurement data.
   4. Vibration Isolation Requirements: Avoid installing the SCXI chassis equipped with SCXI-1349 in areas with continuous strong mechanical vibration, such as near large air compressors, stamping equipment and high-power motors; long-term vibration will loosen the contact needles of the rear signal connector and cause intermittent signal disconnection faults.
   5. Cleaning Maintenance Specifications: Only use dry anti-static soft brushes to clean dust and debris accumulated on the surface of the adapter and connector terminals; water, alcohol, conductive cleaning sprays and other liquid solvents are prohibited to wipe the internal circuit boards and gold-plated connectors, which will cause metal oxidation, poor contact and permanent circuit corrosion damage.
   6. Signal Voltage Usage Limit: Do not transmit analog or digital signals with instantaneous peak voltage exceeding 60 VDC through the adapter’s signal channels; overvoltage will break down the internal PCB insulating layer, cause circuit short-circuit and permanently scrap the SCXI-1349 adapter.