Maximum Sample Rate in Differential Mode Hardware: Multifunction DAQ (MIO)>>E Series, Multifunction DAQ (MIO)>>M Series
Problem: Looking at the specs for my Multifunction DAQ device, I've noticed that there is the option to measure on N channels in a reference single-ended (RSE) configuration, or N/2 channels in a differential configuration. I've also noticed that the sample rate is specified as an aggregate between all the input channels, as there is only a single ADC on this device. Can my Multifunction DAQ device sample at its full rate on one differential channel? Solution: Yes, Multifunction DAQ cards from National Instruments (M Series, E Series, and Compact DAQ) can sample differentially at their maximum rate on a single channel. A differential measurement and a single-ended measurement only differ in the way that the negative terminal of the ADC is connected ( to ch0- and ground, respectively). In both differential and single-ended configurations, the ADC makes only one conversion per channel, therefore input configuration does not affect the maximum sample rate that you can achieve. On the other hand, when measuring multiple channels, whether they are single-ended or differential, the signals are multiplexed into a single ADC which causes the effective per-channel sample rate to be the maximum sample rate of the ADC divided by the number of channels. Related Links: KnowledgeBase 2D6CTML8: Data Acquisition Sampling Terminology KnowledgeBase 30LDURMV: Difference Between the Sample Clock (Scan Clock) and the Convert Clock (Channel Clock) Attachments:
Report Date: 09/25/2006 Last Updated: 09/29/2006 Document ID: 41OGATLA |
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