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AC Amplitude Accuracy of the NI 5122 Digitizer



Hardware: Modular Instruments>>High-Speed Digitizers (Scopes)>>PCI-5122, Modular Instruments>>High-Speed Digitizers (Scopes)>>PXI-5122

Problem:
I am looking at the specification document of the NI 5122, and I can only see the AC Amplitude Accuracy at one frequency (@50 kHz). Where can I find the accuracy specifications for frequencies other than at 50 kHz?

Solution:
The absolute amplitude accuracy is related to the relative passband flatness specification provided in the manual. Our passband flatness spec is shown in the following figure which is an excerpt from the NI PXI/PXIe/PCI-5122 specifications manual. This spec is relative to 50 kHz and hence can be used to determine our amplitude accuracy at frequencies other than 50 kHz. 50 kHz is about where the digitizer's DC and low frequency accuracy transitions to it's high frequency accuracy. This transition is compensated in self calibration, so frequent self calibration (especially with temperature change) is important. With self calibration, frequencies well below the digitizer's bandwidth should be similar in accuracy to 50 kHz although this is not guaranteed.


You would need to add the appropriate relative accuracy spec below to the 50kHz absolute accuracy spec provided under the AC amplitude accuracy section. For example, in the case for filters off, the overall accuracy would be 0.4dB (Passband Flatness Spec) ± 0.09dB(1MΩ) (AC Amplitude spec) = 0.49dB. This is for accuracy measurements across the 20 MHz to 100 MHz bandwidth.

Related Links:
Products & Services: NI PXI//PXIe/PCI-5122 Specifications
Specifications Explained: NI Oscilloscopes and Digitizers

Attachments:


PassbandFlatness.GIF


Report Date: 04/15/2006
Last Updated: 10/04/2017
Document ID: 3WEMERKQ

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