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Updated VI only registers noise, cuts out early
bjw5
Member
06-07-2011 04:48 PM
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Hey,
I recently acquired a set of NI suites (myDAQs, Labview 2010, Multisim) with which to update a student lab for the coming semester. Before this acquisition, the lab used a VI written in Labview 8.2 and carried out on NI-built PCs. To make sure the old lab could in fact be run with new equipment, I loaded the old VI into Labview 2010, adapted the physical system around the myDAQ, and tried to run the VI. On the old machines, running the VI triggers the continuous acquisition of voltage values, which are then fed into a graph and a weighted motor. The user can enter a voltage value at which to run the motor, and altering this value makes a definite impact on the graph and the motor performance.
On the updated machines, however, the graph records noise for 100 values and stops. Graph indicators of the input show continuously generated noise with the same exact physical setup as before. When the user enters a voltage value as before, it has no visible impact, as the motor does not run with the new setup. I have attached the new and old versions of the VI.
The input is the voltage difference across the 2 terminals of the motor, fed into AI0 on the myDAQ, and the output voltage is fed into a custom power supply and amplifier (the same one that worked with the old machine), which then powers the motor itself.
Has anyone encountered similar issues converting VIs? Does anyone know why this graph cuts out early or the input value has no effect? I have double-and-triple-checked the physical setup, and have no idea what I'm doing wrong.
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Aaron O
NI Employee (retired)
06-09-2011 10:33 AM
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bjw5,
I wanted to let you know that this post would be more fitting for the Academic Hardware Products category, which supports myDAQ.
When you say that the VI was written and "carried out on NI-built PCs", do you mean that you were previously using hardware other than a myDAQ, and if so, what hardware were you using?
Can you test the myDAQ from Measurement & Automation Explorer using a Test Panel (Start Menu » All Programs » National Instruments » Measurement & Automation » Left Side Column » Your myDAQ » Test Panel (top button)) and see your analog voltage data?
From here I would suggest that you abstract away from your code and make sure the hardware is working. Testing the code in a Test Panel or using a LabVIEW Example Finder Example (LabVIEW » Help » Find Examples) would be a good first step.
Regards,
Aaron
National Instruments
