04-07-2014 10:42 AM
Hello there,
I had set up a very simple VI for measuring the pressue via a USB-6009 DAQ unit. I had no problems reading voltage from several pressure transducers until just about a week ago. Some strange periodic fluctuations came from nowhere (see attachment). I tried new power supply, new DAQ unit, rewriting the VI. None of this worked. Could someone help me solve this problem?
Thanks,
yanxiang
04-07-2014 01:13 PM
it seems to be some noise. try to take the measuremnt without connecting the sensor and then analyse what you get. if these fluctuations gone then it seems to be problem from your sensor side. one more thing, can you apply on DAQ card some defined analog signal (sine wave etc) and then analyse.
04-07-2014 01:31 PM
Hi Tirmizi,
Thanks for the reply. I have two DAQ cards installed on my computer, one with 3 sensors connected and one with 2 sensors. Every one of them has the same fluctuations. The sine wave singal is a good idea. Will try that out and post the results. That said, I have connected the card directly with two AA batteries, whose voltage should be stable. But that still showed the same fluctuations. Do you think that can be considered as a defined signal?
yanxiang
04-07-2014 01:47 PM - edited 04-07-2014 01:49 PM
What type of process are the pressure transducers measuring? Could it be a real fluctuation in pressure?
EDIT: Just saw your post with the battery test- how long of a run is the wiring for the transducers and for the battery test?
-AK2DM
04-07-2014 02:03 PM
Hi AK2DM,
Sorry if I understood your question wrong, but the lengths of the wires for different sensors vary from ~15" to ~60". For the battery test, I used the 15" wire, perhaps even shorter.
yanxiang
04-07-2014 02:27 PM - edited 04-07-2014 02:43 PM
what you want to say is that you applied a DC volatage (using AA battries) on DAQ card and measure it and have the same fluctualtions. do you process your data means FFT some thing and then display or you display the raw data (time domain).
what happened if you simply take measuremnt from your DAQ without connecting any thing on input and display it. is there still be these flucations present
if you donot find any fluctuations when traking measurement without connecting any signal then the problem lies on sensor/cable or connector side. you have to check for them by changing cable first and then go to sensor
04-07-2014 02:28 PM
04-07-2014 02:42 PM
04-07-2014 02:54 PM
Hi Michael78 and Tirmizi,
Thank you both for suggestions. I have been trying things for the past few days and still experiencing this issue. So I am open to any suggestions. I just restarted the computer but the problem still persists. I have two identical cards running in different VI's and both have this noise. I will try the DAQ card on a labmate's computer and see whether or not I will see the fluctuations.
yanxiang
04-07-2014 02:59 PM
I would check around the lab to see if you have any kind of equipment that works at that period. Like maybe a chamber with a solenoid.