求助多通道ADC输入相互影响的问题

happylj

  I use NI BNC-2110 / PCIe-6363 + Labview 2012 for my DAQ.

In out task, we acquire two analog samples(these two samples are timed by on board clock, 1000000 rate) from each analog input (AI_0 and AI_4) whenever DAQ receives a digital trigger from PFI0 (rising edge and retriggerable). We will receive 200 triggers and our program will finish until we receive 400 samples on each channel.

The interesting thing is that different analog inputs seem to affect each other. As shown in the figure below, the white curve is analog input AI_0 and the red curve is analog input AI_4.  AI_0 is connected to a triangle input and the curve

below seems right. AI_4 is actually shorted (some result if open) but the acquired data is affected by AI_0.

                               
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However, this problem does not occur when only one channel is used in vi (Only the "create channel" and the "read" vi's are changed to be multiple sample and we repeat the experiment with everything else unchanged). So I believe it is not an actual voltage problem before the BNC-2110 board receives the analog input.

Any idea about how to solve this? Thanks in advance! Happy new Year.

sunyuanxin

这个...你是想增大adc的隔离度吗？