The NI SCXI-1122 is a 16-channel isolated multiplexer module engineered for SCXI chassis-based data acquisition systems. It multiplexes multiple isolated analog input channels into a single DAQ device input, expanding measurement capacity while maintaining high-voltage isolation. The module delivers at least 250 Vrms working isolation across independently configurable channels, making it ideal for multi-sensor industrial applications requiring galvanic separation.
Technical Specifications
Channel Configuration
• 16 differential analog input channels in two-wire scan mode
• 8 channels in four-wire scan mode (upper 8 as sense leads, lower 8 as current output)
• 2 isolated excitation channels: 1 voltage source and 1 current source
Isolation Architecture
• Minimum 250 Vrms working isolation
• All 16 input channels isolated from earth ground, but not from each other
• Excitation circuits isolated from earth ground, input channels, and each other
• Independently configurable isolation amplifiers and filters per channel
Excitation Sources
• Voltage excitation (VEX): 3.333 V ±0.04% with 1.0 mA drive capability
• Current excitation (IEX): 1.0 mA source; drives up to fifteen 100 Ω devices in series or eight 5 kΩ devices in four-wire mode
• Voltage source includes internal half-bridge completion and single remote sensing terminal
Signal Conditioning & Filtering
• Integrated 3-pole RC filter with software-selectable bandwidth: 4 Hz (-10 dB) or 4 kHz
• 60 dB noise rejection ratio at 4 Hz bandwidth
• Shunt calibration capability for bridge transducers
• Input impedance: 1 GΩ (powered), 100 kΩ (powered off)
Operating Modes
• Two-wire scan: all 16 channels for input
• Four-wire scan: upper 8 as sense, lower 8 as current output
• Parallel-mode operation supported
– Key Features
• Sensor-agnostic signal conditioning for strain gauges, thermistors, RTDs, thermocouples, millivolt and volt sources, 4–20 mA and 0–20 mA process-current sources
• Software-controlled bandwidth selection optimizes noise rejection vs. measurement speed
• Independent excitation path isolation eliminates cross-channel coupling
– Typical Applications
• Multi-channel bridge transducer measurement
• Thermocouple and RTD arrays requiring isolation
• Industrial process monitoring with galvanic separation
• High-noise environments demanding selective filtering
– Compatibility & Integration
The SCXI-1122 integrates with NI SCXI chassis-based DAQ systems, multiplexing isolated channels into standard analog inputs.
