topic Re: Doubt Regarding Building VI in LabVIEW

Doubt Regarding Building VI

sukumar — Wed, 25 Jul 2007 22:05:08 GMT

I have build a VI that uses a DAQ assistant. The equipment has got DAQ card 6036E. There will be 4 voltage signals that come out from the DAQ card. I want to capture that and display it in 4 different graphs. For that I used the "convert from dynamic data type" and "index array" from the functions palette to split the signals and show it in different graphs. But I dont know what, I am getting the same signal in every graph. I am attaching my file with this message. Please see it and tell me where I had gone mistake. And I am using Labview 7.1 Thanks.

Re: Doubt Regarding Building VI

AnalogKid2DigitalMan — Wed, 25 Jul 2007 22:10:35 GMT

I don't use Express vi's, but I think you can use the Split Signals function under Express pallette. Resize it to 4 outputs, and wire each output to your graphs. No need to convert or index arrays.

Re: Doubt Regarding Building VI

sukumar — Wed, 25 Jul 2007 22:34:30 GMT

i do the procedure you told me to follow. but still i am getting the same thing. the 4 signals are all same. when i test the daq assistant, the 4 signals were different. but when I use with graphs, I am getting this problem. Can u pls solve this problem for me. i am attaching the new file that i have build. Thanks.

Re: Doubt Regarding Building VI

sukumar — Thu, 26 Jul 2007 18:36:04 GMT

i haven't received any reply from you since yesterday evening. so once iam reminding you. so, can u pls help me solve this issue. Thanks.

Re: Doubt Regarding Building VI

Dennis_Knutson — Thu, 26 Jul 2007 19:20:58 GMT

I am able to see different signals with the VI and they match what is seen with the DAQ Assistant test panel. What happens if you connect a graph directly to the output of the DAQ Assistant so that all 4 are displayed on the same graph?

Re: Doubt Regarding Building VI

EdDickens — Thu, 26 Jul 2007 20:18:50 GMT

Your DAQ Assistant is setup correctly to read four different channels and you are slpitting them correctly to the graphs. There's no configuration issues here.

Are you sure the signals connected to the four channels are different enough that you can see a difference?

Re: Doubt Regarding Building VI

sukumar — Thu, 26 Jul 2007 21:53:42 GMT

Reply for Dennis:

I was able to see the signals on a single graph but it would be clear if they were on different graphs so that we can measure and do analysis on them individually. can you suggest me how to acheive it? Thanks.

Re: Doubt Regarding Building VI

sukumar — Thu, 26 Jul 2007 21:58:47 GMT

Reply for Dickens:

I am very much sure that the 4 signals are different since we had measured it with the other software and they are dissimilar. So, I want to ask you can u tell me the solution for it. Thanks.

Re: Doubt Regarding Building VI

Dennis_Knutson — Thu, 26 Jul 2007 22:40:03 GMT

If the signals are dissimilar on the graph with all four displayed, the VI you have with the Split Signals will display 4 separate dissimilar signals. You don't have to do anything else.

If you don't see dissimilar signals on the 4 separate graphs and do and the one with all 4, run the VI so that you have signals on on graphs. Stope the VI and go to the Edit menu and select Make Current Values Default. Save the VI. Post that VI.

Re: Doubt Regarding Building VI

sukumar — Tue, 31 Jul 2007 22:41:52 GMT

I am posting the VI you asked for. The second, third and fourth graphs almost look the same. I can find it wrong because the signals are coming from the electrode and if I touch one electrode that should change only one signal but here it is changing all signals and they are randomly coming. But this is not with the software of the device. Can u pls look at it and give me a solution. Thanks.

Re: Doubt Regarding Building VI

sukumar — Tue, 31 Jul 2007 22:46:57 GMT

And also this is with one another method. Here also the same problem that the signals are not coming correctly. And here there is no signal from the fourth channel itself. Can u pls solve me this problem. Thanks.

Re: Doubt Regarding Building VI

EdDickens — Tue, 31 Jul 2007 23:05:28 GMT

I'm going to have to say that there is a wiring problem somewhere. None of the VI's you have posted would cause the same signal to show up in the graphs.

Things to look for in the wiring. You have the DAQ assistant setup to read the signals as Differential signals. This means you should have a high side and a low side signal wire coming from each signal. For example, if you are using one of the standard NI terminal blocks, the signal for channel 0, the high side should be on terminal 68 and the low side should be on 34. Channel 1 should be high on 33, low on 66. Channel 2 should be high 65, low 31. Channel 3 should be high 30, low 63.

If these are all connected correctly, then you may have some cross talk in the wires going to the terminal block or a grounding issue some where else.

Check these and let us know what you find.

Re: Doubt Regarding Building VI

sukumar — Tue, 31 Jul 2007 23:15:54 GMT

those are not the differential signals. they all are different. I don't find any mistake in wiring since u may see its all clear, no overcrossings. And the same setup when I use with the other software that it comes with its working fine. Can u tell me what exactly could be the problem. Please once more have a look at it. Thanks

Re: Doubt Regarding Building VI

Dennis_Knutson — Wed, 01 Aug 2007 00:20:34 GMT

This whole thread seems to be pointless. You did not do what I asked in posting a VI with actual signals. Also, everyone who has looked at your VI has found nothing wrong with the code. If you have a problem with acquiring the signals, then it a problem with your configuration or the physical wiring.

Re: Doubt Regarding Building VI

sukumar — Wed, 01 Aug 2007 00:27:54 GMT

i have posted the VI. is that not the one u were asking for. I ran the program and stopped and then saved the file which I have posted earlier. what do u mean by posting VI for actual signals? Thanks.

Re: Doubt Regarding Building VI

Dennis_Knutson — Wed, 01 Aug 2007 01:23:42 GMT

You should carefully read what I asked before and I will repeat it - step by step. First, you need to add a graph for the un-split signal. This means adding an indicator right before the Split Signal function. Run the VI until you see a signal on the graphs. Now comes the important part and what you did not do before. Go to the Edit menu and select Make Current Values Default. Save the VI. Post it. It might be a good idea to close LabVIEW and re-open the VI before you post it. If there are no signals on the graphs, you did it wrong again.

Re: Doubt Regarding Building VI

sukumar — Wed, 01 Aug 2007 16:49:18 GMT

i dont see "make current values default" in the edit menu. I am using Labview 7.0. can u pls tell me where can i find it. Thanks.

Re: Doubt Regarding Building VI

Dennis_Knutson — Wed, 01 Aug 2007 17:12:32 GMT

In 7.0, it's under the Operate menu.

Re: Doubt Regarding Building VI

sukumar — Wed, 01 Aug 2007 17:25:05 GMT

hey here is the VI you asked for..waveform 9 is the unsplit signal. can u tell me now what's the problem would be? Thanks.

Re: Doubt Regarding Building VI

Dennis_Knutson — Wed, 01 Aug 2007 17:54:26 GMT

THERE IS NO PROBLEM. Each of the individual graphs is showing exactly the same signal that is on the graph with all 8. Do you not realize that each of the 8 graphs is autoscaling the y axis? Just look at the scale numbers on the y axis. Can you not tell that the graph with all 8 is going from .08 to -.04 volts and for example, waveform graph 4 is going from .03 to 0 volts? That's pretty basic. If you want the same scale for all channels, turn off autoscaling and set the y axis values to be the same on all 8.