Difference Between NI 4472 and NI 4472B Hardware: Modular Instruments>>Dynamic Signal Acquisition and Analysis (DSA)>>PXI-4472B
Problem: What is the difference between the NI 4472 DSA device and the vibration-optimized NI 4472B DSA device? Solution: When measuring a signal in AC coupling mode, the DSA board adds a high-pass resistor-capacitor (RC) filter into the positive and negative signal paths to eliminate the DC component of a signal. The difference between the NI 4472 and NI 4472B is the cut-off frequency ofthe high-pass filter.
This enables the 4472B to take very low frequency vibration measurements. . Below is the frequency response of the NI 4472:
The frequency response of the NI 4472B is the same as above except it is shifted to have a -3dB point of 0.5Hz. The filter time constant is 47 ms for the NI 4472. The high-pass RC filter settles to 0.5% accuracy in 0.25 s in response to a step input. It takes 0.782 s to settle to 24-bit accuracy in response to a step input. The settling time is somewhat dependent on the DUT impedance as well. The NI 4472B has a larger time constant (330 ms). It takes 5.5 s to settle to 24-bit accuracy in response to a step input. Note: The response to a step is referring to the DC offset of the signal. DSA boards are designed for Dynamic signals and take some time to settle a DC offset. Please refer to the Dynamic Signal Acquisition Help linked below for more details. Related Links: Products and Services: PCI 4472B Product Manuals: NI Dynamic Signal Acquisition User Manual (June 2007) KnowledgeBase 1H59Q2W3: Basic Information about AC and DC Coupling KnowledgeBase 0HFCAC1J: How Large a DC Offset Can I Remove with AC Coupling on My Dynamic Signal Acquisition (DSA) Device? KnowledgeBase 2W7AQONQ: Why Do I see a Voltage Offset When I Have AC Coupling Set on My NI-4472? Attachments:  - img1.JPG
Report Date: 09/18/2006 Last Updated: 09/22/2008 Document ID: 41H3DUQ2 |
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