Why does changing Sampling Rate (Hz) in 9206 DAQ change values being obtained? Help

[jffernandez]

I am running a VI with a DAQ 9206 obtaining several readings from a PT and CT. Some background, I am running labview 2010, with the NI DAQ 9206 connected to a network via ethernet.

When I change the sampling rate (Hz) my values being read in labview change. For example, I am reading voltage signals from a system, when I change the Frequency to 12KHz, I get a reading of 119V. When I change the sampling rate to 9 KHz, LabView reads 122 V. At 6 KHz, I read 125 V.

Why is there a change in value in LabView? Nothing has been altered on the hardware in between changes on the sampling rate.

Any help or explanation would be greatly appreciated.

[Stefo]

Hi jffernandez,

hm, I can't explain for sure, but one possible explanation could be that you have higher impedance source, which doesn't allow signal to settle. In that case, slower you measure, more precise result you get - but take it just as theory. Input impedance of the module is >10GOhms, 100pF.

regards,

stefo

[micahmcc]

It sounds kind of like a settling issue to me as well. 

jffernandez, what value are you expecting to read?

I think a diagram showing how you are connecting your sensors and configuring your measurements will help us get a better idea of what is happening. If you want to reply to this thread and include some wiring diagrams along with more info on what sensors you have, I would be happy to look into your issue some more.

Let me know!