With 118 dB dynamic range and low noise and distortion, NI 446x

devices can make very accurate frequency-domain measurements. They

have excellent amplitude flatness of ±0.1 dB within the frequency range

of DC to 92 kHz, and have a typical THD of -107 dB.

Antialiasing

The analog inputs have both analog and digital filters implemented in

hardware to prevent aliasing. Input signals are first passed through a fixed

analog filter to remove any signals with frequency components beyond the

range of the ADCs. Then digital antialiasing filters automatically adjust

their cutoff frequency to remove any frequency components above half the

programmed sampling rate.

Analog Outputs

NI 4461 devices have two channels of 24-bit resolution, high-fidelity

analog output. A common application of the analog output is to stimulate

a system under test while measuring the frequency response with the

analog inputs. The output conversions occur simultaneously at software-

programmable rates up to 204.8 kS/s. The analog output circuitry uses

8-times oversampling interpolators with 64-times oversampling delta-sigma

modulators to offer exceptional spectral purity. Software-programmable

attenuation of 0, 20, or 40 dB is available on the output channels. NI 4461

devices have excellent amplitude flatness of ±0.1 dB within DC to 92 kHz,

and a THD of -95 dB at 1 kHz. You can simultaneously acquire data on the

input channels while updating the output channels.

Anti-Imaging

NI 4461 output channels have both analog and digital anti-imaging

filters. These filters remove the unwanted out-of-band components

generated when an analog signal is produced from digital data.

The digital filters limit the bandwidth of the output signal to half the

original conversion rate, thereby rejecting images caused by the 8-times

oversampling process. The signals generated by the analog output

circuitry are low-distortion, low-noise, flat-frequency analog signals.

Multimodule Synchronization

For applications requiring more channels, you can synchronize the operation

of two or more NI 446x devices with less than 0.1 deg phase mismatch.

Synchronization is achieved by sharing a digital trigger and clock between

multiple modules. The NI-DAQmx driver software automatically handles the

synchronization of multiple devices in a single task.

Triggering

NI 446x devices offer both analog and digital triggering for signal

acquisition. The source of the trigger can come from any analog input

channel, the external digital trigger input, the PXI trigger bus (PXI devices),

or the RTSI bus (PCI devices). The external digital trigger is 5 V

TTL/CMOS-compatible and is activated by a choice of rising or falling edge.

Triggering is needed in applications that acquire transient signals. When

performing structural analysis by striking a metal beam with a hammer, for

instance, you measure transient vibrations with accelerometers with

acquisition triggered by the hammer impact.

Calibration

National Instruments calibrates the offset voltage and gain accuracy of the

analog inputs and outputs. An onboard precision voltage reference ensures

that the gain and offset remain stable and accurate. NIST-traceable and

ISO 9002-certified calibration certificates are available on request.

Software

NI Measurement Services Software

NI 446x devices use NI measurement services software, based on the

NI-DAQmx driver, as the hardware and OS interface. You can build

automated test systems or integrate an NI 446x with other hardware,

including modular instruments and multifunction data acquisition (DAQ)

products, through NI-DAQmx function calls. NI measurement services

software also includes DAQ Assistant, an interactive guide that steps

you through configuring, testing, and programming measurement tasks

and generates the necessary code automatically for National

Instruments LabVIEW, LabWindows/CVI, or Measurement Studio.

Analysis Software

LabVIEW Sound and Vibration Toolkit

NI 446x devices are well-suited for audio, acoustic, and vibration

analysis applications. The LabVIEW Sound and Vibration Toolkit

incorporates Express technology to make it easier for you to perform

sound and vibration measurement and analysis. The toolkit includes

LabVIEW Express VIs for:

• Fractional-octave analysis with weighting

• Integrated vibration level

• Weighted sound level

• Zoom power spectrum

• Peak search

• Power in band

24-Bit, 204.8 kS/s Dynamic Signal Acquisition and Generation

2

BUY ONLINE at ni.com or CALL (800) 813 3693 (U.S.)

Figure 2. With application software such as NI LabVIEW, you can conduct

frequency-response, swept-sine, and other common audio measurements.