National Instruments 779688-01 PXI Sound and Vibration Module

The National Instruments 779688-01 belongs to the PXI‑4462 Model series, which is designed primarily for high-accuracy sound and vibration applications. With the four channels of dynamic signal acquisition this module offers, accurate frequency-domain measurements are made possible. It has software-configurable AC/DC coupling, IEPE conditioning, and six gain options for adjusting the input range. Because of this, it can be used with large dynamic range transducers, such as accelerometers and microphones. Audio testing, machine condition monitoring (MCM), and vehicle noise, vibration, and harshness (NVH) analysis are examples of common applications.

With 24-bit resolution ADCs, the 779688-01 lets you perform simultaneous sampling at programmable rates of up to 204.8 kS/s. These programmable rates (44.1 kS/s, 48.0 kS/s, 96.0 kS/s, and 192 kS/s) are useful for standard audio applications like CD players and digital audio equipment. To ensure the best possible analog readings, the analog inputs also have programmable AC/DC coupling and a gain amplifier stage with options from -20 to +30 dB in 10 dB steps. The module achieves a dynamic range of 118 dB with little noise and distortion, supporting both single-ended and differential signal connections. With an amplitude flatness of ±0.1 dB and an average THD of -107 dB, the frequency range covers DC to 92 kHz.

The 779688-01 includes two channels of 24-bit-resolution analog output. These outputs are necessary for stimulating systems under test while measuring frequency response with the analog inputs. Exceptional spectral purity is achieved by employing 64-times oversampling delta-sigma modulators and 8-times oversampling interpolators to achieve output conversion rates of up to 204.8 kS/s. A THD of -95 dB at 1 kHz and an amplitude flatness of ±0.1 dB are displayed via the analog output channels, which can be adjusted for attenuation of 0, 20, or 40 dB. Unwanted out-of-band components produced during the digital-to-analog conversion process are removed by the output channels' analog and digital anti-imaging filters.

If more channels are needed for an application, sharing a digital trigger and clock allows multiple NI 446x devices to be synced with less than 0.1-degree phase difference. The synchronization process is made easier by the NI-DAQmx driver software.