Why the acquisition with DAQmx is different by using Labview 8.2 from Labview signal express?

[stage84]

Hello,

I am using a PCi-6281 to acquire a voltage. When I am using Labview signal express with only the step to acquire I read the good signal with the exact voltage. But when I am using my VI, the y axis and the values recorded are wrong. Why this difference appears?

I insert a picture with both signal: at the top is the signal from my vi (wrong measurement) and at the bottom is the signal from labview signal express (correct).

The vi I am using is the example Cont Acqu&Graph Voltage-To file (binary).vi.

Thank you for your answer!

Sophie

Sophie

[RavensFan]

Why are you using the Binary File version?  What you are getting is the binary data, saved in I32 rather than the values scaled to Voltage like the express VI is doing.

If you look at the options for DAQmx read, you will see you are set for unscaled data 2D I32.

[stage84]

I am using the binary file because it requires the minimum change in another VI. I have tried to change in scaled data but now my second VI has not enough memory to display all data.... What's wrong? Here is my second VI. Totest with data you need to insert a number in the "scaling factor" if not the dat are multiplied by zero...

thanks for your help!

Message Edité par stage84 le 07-24-2009 10:11 AM