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Why do I get Channel Interference and Non-Isolation?

Hardware: Multifunction DAQ (MIO)>>Portable>>USB-6215

Problem: I have a voltage source hooked up to a single channel, but the other channels are getting the same reading when they are supposed to be zero.

Solution: To eliminate the channel interference, short (connect the + terminal to the - terminal) the channels not being used. The reason that the channels are obtaining incorrect readings when they are not shorted is because they are floating. This means that they are retaining their last value and not giving out a new value of 0.

Also, unless you have something explicitly plugged into a channel, you can consider the reading false because it is not getting that value from anywhere specific and may or may not be correct.

For this example, we will consider channel 1 to have a 2V source, and channels 2,3, and 4 to have no source.

  1. At first, when reading the inputs, we see 2V on all channels (1-4).
  2. Short (connect + to -) for channels 2,3,and 4. Now read inputs again. The inputs should read 2V for channel 1, and 0V for channels 2,3,and 4.


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Report Date: 10/09/2006
Last Updated: 10/24/2006
Document ID: 428C3AN5

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