Hi there!
I have a problem with a school project I'm working on. The situation is that we have to measure the signal of an accelerometer. It's connected to a power supply/coupler, wherefrom it's connected to a NI 9221 module's AI0 port. The 9221 is in a cRIO-9074 which is connected to the PC with Ethernet. We checked the accelerometer with an oscilloscope, that's OK.
With LabVIEW I wolud like to display the signal on a waveform chart. So I've created a real-time project, and added the cRIO-9074 and the 9221 in it. I dragged and dropped the AI0 in the VI where the signal is connected on the module and connected it to a waveform chart.
If I run the VI there is somekind of signal, but it's not what it should be. I can set the number of pulses /min, by setting the revolution of the electric motor whose shaft keeps hitting the rod (which on the accelerometer is glued) once a revolution, so I know what kind of signal form should I expect. But the expected and the result signal doesn't match at all. I expect rhytmically iterating pulses, but what I see isn't rhytmical at all, and the positive/negative peak value of the signals aren't nearly constant too. It looks like it's almost random. I have the feeling like this is a sampling synchronization problem, but I don't really know. It seems like that the sampling of the module and the software only meets randomly, and that's why I rarely get one-one good pulse form on the chart.
I tried to put the whole thing in a TimedLoop and set the Source type to: Synchronize to Scan engine, but it didn't help. I tried to change the value of the Period and Priority too, but it didn't change nothing. I also tried to change the parameters of the Scan engine in the MAX at the properties of the cRIO-9074, but it's the same situation.
Another thing is I tried to save one measurement file to the cRIO's memory witht the Write to Measurement file. When I tried to open it I saw, that there are only about 200.000 samples in it, although I have measured for mor than 3-5 seconds. As I know the 9221 has a 800kS/s sampling rate so I have no idea.
I would be grateful if anyone could help me with this problem, because I'm running out of ideas, and I can't step forward until we can't measure acceptable results.
Best regards,
Tschabee91
