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I'am trying to acquire DC voltage using NI 6009,

i have made NI-DAQmx tasks.


i cannot get the accurate value because of the -1.14 value when i run the vi.

what can i do to get rid of this value and acquire the exact value from external source.



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What makes you think that's not the correct value?


If all you want is to remove some offset voltage, consider searching for "tare" functionality examples on the forums.


The basic idea would be to measure the voltage at some time when you'd like to call the result zero, then store that value in a Shift Register. Subtract the value in the shift register from every subsequent measurement when you expect non-zero values.


See here for a simple example using a Feedback Node instead of a shift register:

GCentralI'm attending the GLA Summit!
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I'm not sure why, but I cannot open your VI.  The USB-6009 isn't bad at measuring voltages in the ±10v range, but you need to understand some elementary Electrical Engineering (like the difference between single-ended and differential inputs to an A/D converter, and how grounding works) to get the most reasonable values.  I agree with @cbutcher -- how do you know the value -1.14 is incorrect?  My guess (without being able to see the code nor understand how the device has been configured) is that the problem is in the "wiring" (and by "wire" I mean copper, not a LabVIEW Data Wire).


Bob Schor



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