I. Product Introduction

NI SCXI-1304 is an 8-channel configurable AC/DC coupling terminal board for the SCXI platform, not a data acquisition module, specifically designed for the SCXI-114x series (such as 1140/1141) high-precision voltage input modules. The core feature is that each channel has independent AC/DC coupling + 100kΩ bias resistor for grounding, suitable for floating signal sources and AC small signal measurements. It is now discontinued and spare parts and technical support are available.

II. Model Interpretation

SCXI: Instrument Signal Conditioning Expansion Series

1304: Basic model, representing an 8-channel AC/DC coupling terminal board

Part Number: 777687-04, 185963A-01

Series Positioning: 1304 (AC/DC coupling) → 1305 (with BNC AC/DC coupling), focusing on AC/floating signal conditioning search.ni.com

III. Technical Parameters

Electrical Parameters

Channel Configuration: 8 differential inputs (compatible with SCXI-114x)

Terminal Type: Screw Terminal (inside the shielded enclosure), no BNC

Coupling Configuration: Each channel has a 2-bit dip switch, AC (high-pass filtering)/DC (direct connection) selectable

Bias Grounding: Built-in 100kΩ resistor for each channel, switchable for grounding, providing a reference for floating sources

Wire Specifications: 26–14 AWG

Rated Voltage: ±10V (signal to ground)

Insulation Resistance: ≥1MΩ (500V DC)

Common Mode Suppression Ratio (CMRR): ≥100dB (DC～60Hz)

Mechanical and Environmental

Size: 198.1×76.2×111.8mm

Installation: Standard SCXI front panel / compatible DIN rail

Operating Temperature: 0～50℃; Storage - 20～70℃

Humidity: 10%～90% without condensation

Shielding: Full metal shielding enclosure, anti EMI/RFI interference

IV. Interface and Communication Configuration

Front Panel: 8 differential screw terminals, shielded ground, channel configuration dip switch (2 per channel)

Back Panel: 96-pin DIN connector, direct connection to the front end of the SCXI-114x module, no independent communication bus

Software Support: Compatible with NI-DAQmx driver, compatible with LabVIEW, C/C++, LabWindows/CVI

V. Core Functions

Independent AC/DC Coupling per Channel: AC mode enables high-pass filtering to remove DC components and low-frequency noise, suitable for vibration, acoustic, etc. AC signals; DC mode direct connection, suitable for DC/variable signals.

Floating Signal Ground Reference: 100kΩ bias resistor for grounding, providing a stable reference for non-grounded (floating) sensors, reducing common-mode interference and signal drift.

Full Shielding Anti-Interference: Metal enclosure + internal isolation design, suppressing EMI/RFI in industrial environments, ensuring stable measurement of weak AC signals.

Flexible Configuration and Reliable Wiring: Dip switch for on-site quick configuration, no software required; Screw terminals compatible with multiple wire specifications, anti-vibration and anti-loosening.

VI. Application Scenarios

AC Small Signal Measurement: AC signal acquisition for vibration sensors, microphones, accelerometers, etc. (compatible with SCXI-1141 high-sensitivity module).

Floating Sensor Measurement: High-precision measurement of non-grounded sensors (such as isolated piezoelectric sensors).

Industrial Strong Interference Environment: Signal acquisition near motors, frequency converters, etc., shielding + common-mode suppression ensures stability.

SCXI-114x Companion System: Combined with 1140/1141 modules to build an 8-channel high-precision voltage acquisition system.

VII. Usage and Maintenance Instructions Instruction Manual

Power-off installation: Align the module front and push it in smoothly to ensure that the 96-pin connector is fully attached and the locking mechanism is fixed.

Configuration of jumpers: For each channel, set 2 switches to AC or DC simultaneously; the grounding switch should be closed as needed (floating sources are recommended to be closed).

Wiring standards: The positive and negative ends of the differential signal correspond to the terminal labels, 26–14 AWG wires, tighten the screws; the shielded end connection system is grounded.

Software configuration: Select the corresponding module in NI-DAQmx, set the input range and sampling rate, no additional drivers required.

Maintenance instructions

Environment: Maintain ventilation and dryness, temperature 0-50℃, away from dust, corrosive gases and strong electromagnetic interference.

Regular inspection: Check for loose terminals, oxidation, rust, and damaged insulation of the wires monthly; promptly tighten or replace if necessary.

Cleaning: After power-off, wipe the terminals and the casing with water-free alcohol, dry and then power on; do not allow liquids to enter the connector.

Fault diagnosis: When there is abnormal signal, prioritize checking the jumper configuration, wiring, and shield grounding; poor connector contact is mostly due to dust or oxidation.

Long-term storage: After power-off, remove the terminal board, clean the terminals, seal with an anti-static bag, and store in a cool and dry place.