Why Do I Get Bad Readings from My E Series Board with NI-DAQmx Base? Primary Software: Driver Software>>NI-DAQmx BasePrimary Software Version: 2.0.1 Primary Software Fixed Version: N/A Secondary Software: N/A Hardware: Multifunction DAQ (MIO)>>E Series
Problem: I have a program written in NI-DAQmx Base that performs hardware-timed analog input on my E Series DAQ board. Why does the graph of my signal look incorrect? Solution: One thing to watch for when using NI-DAQmx Base with an E Series board is to make sure that you have specified a valid Sample Clock rate. NI-DAQmx Base does not throw an error until the Sample Clock rate (aggregate sampling rate - i.e. the rate at which the ADC runs) exceeds 6.66 MHz, which is well beyond the capabilites of any NI DAQ board. If the Sample Clock rate is set to a value above the actual limit of the device, the ADC on the board will not have time to settle properly between samples, resulting in a distorted waveform. Make sure that the Sample Clock rate does not exceed the specified limit of the board, and the measured signal should be correct. Keep in mind that the sampling rate specified in your program is the per channel rate (Samples per Channel per Second). The Sample Clock rate (aggregate sampling rate) is the sampling rate specified in your code times the total number of channels. For more information on sample clock terminology, see the related link below. Related Links: KnowledgeBase 2D6CTML8: Data Acquisition Sampling Terminology Attachments:
Report Date: 05/08/2006 Last Updated: 05/12/2006 Document ID: 3X7G69E1 |
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