Can not measure temperature and voltage simultaneously

Question

I am a beginner with labview. I want to measre temperature and voltage simultaneously. When I run
the VI, I can get temperature or voltage, but not togther. I attach my VI, please give me suggestion on
how to make it work. 3X
Attachments:
heatflux.vi ‏1069 KB

Answer 1

Since I don't know your exact configuration I will make some basic assumptions based on how it appears that you have configured the DAQ Assistant Express VIs.
Assumptions:
1. You have only one DAQ board in your system.
2. You want to scan continously
3. You want to acquire 3 temperature channels at a rate of 1000S/s and take 100 readings at a time
4. You want to acquire 2 voltage channels at a rate of 1000S/s and take 1000 readings at a time.
Based on this configuration your first problem is that you have configured the DAQ board to acquire continously in the first call to the DAQ Assistant (your first frame of the sequence structure). This ties up all the analog acquisition resources without releasing them. When you make your second call to the DAQ Assistant (your second frame of the sequence structure) you are creating a conflict because the DAQ board is already busy running your first request. At this point you are probably receiving an error but you might not see this since you are not doing error checking in your code. This is also why you are only getting one set of data. Next iteration of the while loop the first call to the DAQ Assistance reconfigures the board and executes again and so the cycle repeats itself.
I don't have a DAQ board installed so I can't confirm with certainty if I am correct but you can do this by simply changing the DAQ Assistant properties. In the 'Task Timing' tab change from 'Acquire Continuosly' to 'Acquire N Samples'.
Assuming this works all you have done is confirmed that my assumptions are correct and technically your program should work. So now some programming advice.
It's ok to scan all channels at once even though they might not be of the same type so go ahead and configure all your channels in one DAQ Assistant call and get rid of the sequence structure. Decide on one set of parameters for Scan Rate and Samples to Read, in your case I doubt this will be a problem. Since you are performing the same analysis on all channels you don't need to parse your data simply pass the 'data' from your DAQ Assistant into a single 'Amplitude and Level Measurements' Express VI. You will now have a single array with all your Mean values based on the order the channels are configured. If you want to plot the data in different graphs all you need to do is parse your channels using the 'Split Signals' or 'Select Signals' Express VI.
Hope this makes some sense.
-Christer