The NI PXI-6221 is a 16-bit M Series multifunction data acquisition module for PXI systems, delivering synchronized analog input, analog output, digital I/O, and counter/timer functionality. It acquires up to 16 single-ended or 8 differential analog channels at 250 kS/s aggregate sampling rate with programmable input ranges (±0.2 V, ±1 V, ±5 V, ±10 V) and exceptional common-mode rejection of 92 dB. The module provides two 16-bit analog outputs at 833 kS/s update rate, 24 lines of digital I/O with TTL/CMOS logic levels and individual direction control, and two 32-bit counters operating at up to 80 MHz. Input FIFO capacity reaches 4,095 samples with 4,095-entry scan list memory for efficient data streaming. Overvoltage protection extends to ±25 V on powered inputs and ±15 V when offline, with ±20 V protection on digital I/O pins. The 700 kHz input bandwidth and 16-bit resolution support high-fidelity measurements in automated test, data logging, process control, and research environments. NI-DAQmx driver integration enables development in LabVIEW, LabWindows/CVI, and Measurement Studio, while SCC and SCXI signal conditioning modules extend measurement scope.
Technical Specifications
Analog Inputs
• 16 single-ended or 8 differential channels
• 16-bit resolution with 250 kS/s single-channel and aggregate maximum
• Programmable ±0.2 V, ±1 V, ±5 V, ±10 V ranges per channel
• 92 dB common-mode rejection (DC to 60 Hz)
• 700 kHz small-signal bandwidth
• Input impedance >10 GΩ || 100 pF when powered; 820 Ω when offline
• ±25 V overvoltage protection (powered); ±15 V (offline); ±20 mA maximum input current during overvoltage
• ±100 pA input bias current
• Crosstalk: -75 dB adjacent, -90 dB non-adjacent at 100 kHz
• 4,095-sample FIFO and 4,095-entry scan list
Analog Outputs
• 2 channels, 16-bit resolution
• 833 kS/s update rate with 6 μs full-scale settling time
• ±10 V output range
Digital I/O
• 24 channels, individually programmable input/output
• TTL/CMOS logic, 24 V digital logic levels
• 1 MHz hardware-timed operation on up to 8 correlated lines
• 24 mA current drive for relay and actuator control
• ±20 V input protection on up to two pins
• 50 kΩ typical pull-down resistance
Counters/Timers
• 2 channels, 32-bit resolution
• 80 MHz maximum clock rate
• 10 MHz and 100 kHz base clocks with 1–16 divisors
• 50 ppm base clock and timebase accuracy
• Pulse generation supported
– Key Features
• 16-bit measurement and generation resolution across all signal types
• High input impedance (>10 GΩ) minimizes loading on measured signals
• Hardware-timed correlated digital I/O for synchronous control
• Extensive overvoltage and input protection for harsh environments
• Scan-list-based channel sequencing for flexible measurement patterns
– Typical Applications
• Automated test equipment and production monitoring
• Multi-channel data logging and acquisition
• Real-time process control and feedback systems
• Industrial measurement and sensor integration
– Compatibility & Integration
NI-DAQmx driver support enables development in LabVIEW, LabWindows/CVI, and Measurement Studio. Signal conditioning via SCC and SCXI modules expands measurement capabilities for conditioning, signal isolation, and channel expansion.
