PXI-4461: Product OverviewThe National Instruments PXI-4461 is a 4-channel dynamic signal acquisition (DSA) module designed for the PXI platform, specializing in high-resolution measurement of audio, vibration, and acoustic signals. This module functions as a precision digitizer for applications requiring wide dynamic range and low-noise performance, such as sound pressure level measurements, structural vibration analysis, and electro-acoustic testing. Its primary role is to condition and digitize analog signals from microphones, accelerometers, and other transducers with exceptional amplitude accuracy.Installed in a PXI chassis, the module operates by simultaneously sampling all four input channels using delta-sigma analog-to-digital converters, ensuring precise phase alignment between channels for cross-channel measurements like frequency response and transfer function analysis. Each channel provides software-selectable AC/DC coupling and IEPE (Integrated Electronics Piezo-Electric) constant current excitation for powering ICP®-type sensors without external signal conditioning. The anti-aliasing filters are automatically optimized for the selected sample rate, providing protection against out-of-band signals while maintaining passband flatness. The combination of high resolution and simultaneous sampling makes it suitable for applications where both amplitude accuracy and phase relationship between channels are critical.
NI PXI-4461
PXI-4461: Technical Specifications
• Model Number: PXI-4461
• Manufacturer: National Instruments
• Product Type: Dynamic Signal Acquisition (DSA) Module
• Number of Channels: 4 simultaneously sampled channels
• Resolution: 24 bits
• Maximum Sampling Rate: 204.8 kS/s per channel
• Dynamic Range: 118 dB typical
• Input Coupling: Software-selectable AC/DC
• IEPE Excitation: 2 mA or 4 mA constant current, software-selectable
• Triggering: Analog, digital, and software triggering
• Operating Temperature: 0°C to 55°C
• Relative Humidity: 10% to 90% non-condensing
NI PXI-4461
Core Features & Customer ValueHigh Dynamic Range and Resolution: The 24-bit resolution provides 16,777,216 discrete quantization levels, enabling accurate measurement of very small signals in the presence of large signals. The 118 dB dynamic range allows users to characterize low-level harmonic distortion products and noise floors without range switching. For audio testing applications, this enables precise total harmonic distortion (THD) and signal-to-noise ratio (SNR) measurements that meet international standards.Integrated IEPE Signal Conditioning: The built-in constant current sources (2 mA or 4 mA) power ICP® sensors directly, eliminating the need for external signal conditioning modules. This simplifies system integration for vibration and acoustic measurements using piezoelectric transducers. The software-selectable current source allows optimization for different sensor types and cable lengths, ensuring reliable operation across various measurement scenarios.Anti-aliasing Protection: The automatic anti-aliasing filters adjust their cutoff frequency based on the selected sample rate, providing protection against out-of-band signals while maintaining passband flatness. This eliminates the manual filter selection required with traditional spectrum analyzers and ensures valid measurements across the entire frequency range. The steep filter roll-off (>90 dB stopband rejection) prevents aliasing errors that can corrupt frequency domain measurements.Typical ApplicationsIn electro-acoustic testing, the module measures frequency response, harmonic distortion, and sensitivity of microphones, speakers, and headphones in accordance with IEC 60268 and other audio standards.For structural health monitoring, it acquires vibration data from accelerometers mounted on machinery, bridges, or buildings, supporting modal analysis and condition-based maintenance programs.In noise, vibration, and harshness (NVH) testing, the simultaneous sampling capability enables sound intensity measurements using paired microphones and transfer function analysis between noise sources and vibration points.
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