data aquisition using scxi-1530

[jc288]

I am having problems using the scxi-1530 accelerometer DAQ card. To begin, I will explain my setup. I am using this daq card in my chassis connected to my PCI card in my computer. I have created an acceleration VI using the DAQ assistant. Within the DAQ assistant, I have entered all of the information about my accelerometer; i.e. the sensitivity, etc. My accelerometer is a PCB Piezotronics 352C67 model accelerometer.

 Once I have built the VI and run it, sometimes I get results out the accelerometer whenever an acceleration is imposed on it and sometimes I get nothing out of it, even though I have not changed anything in the VI. I am also troubled by what type of sampling rate I need to have set for the program. I am having a lot of trouble on such a seemingly simple task. There is not much to the VI, but I cannot get concrete results out of it. Is there anyone with any help or ideas that may help me in my situation. Thanks.

[CKap]

Hello Jc,

Which PCI card do you have connected to the SCXI Chassis? And also, which DAQ driver (and version) are you currently using? These inputs would help in troubleshooting your problem. I have also attached a snapshot of the DAQ assistant indicating what I think should be its correct configuration. Also could you please post your VI, so that it can be referred to?

The sampling rate that you need to define for your application depends upon the actual signal that you are trying to acquire. If the highest frequency component in the signal is X Hz then you should at least sample at 2*X Hz. But ideally you would want to sample about 5 times.

Chetan K

Application Engineer

NI

[jc288]

CKap,

The PCI Card I am using is a PCI-6034E series card. The DAQmx driver I am using is v7.2 and the DAQ software version is 7.2 as well. My chassis is SCXI 1001 is that makes any difference. I am attaching screenshots of my VI and the vDAQ virtual assistant.

Below is the link to the spec sheet for the accelerometer for further information about it.

http://www.pcb.com/spec_sheet.asp?model=352C68&item_id=7266

Any information you may have would be greatly appreciated.

Thanks.

[CKap]

Hello jc,

How are you supplying excitation to the Accelerometer? I see that you have selected "External" as the Iex source. Ideally it should be set to "Internal" so that the SCXI-1530 can supply current to it. 

Also you don’t need to sample so fast, a sampling rate of 10 KHz should be fine with “samples to read” defined as 1000. After making these changes, click on the "Test" button in your DAQ assistant to check and see if the setup is working correct.  

 

The numeric indicator wired to the loop-iteration counter does not represent the number of data points collected, so the current display would be incorrect.

 

I modified an example program to suit this application. Please define the corrent physical channel as per your setup.

Chetan K

Application Engineer

NI

 

[jc288]

Ckap,

I tried this VI and it wouldn't open. The message that came up was that the VI version (7.1) is newer than the LABVIEW version (7.0). Sorry if I may have mentioned the wrong version before. I didn't look up the version of Labview itself. Would you be able to resend the VI in another version?

Thanks.

[GDE]

JC,

I had a couple of “quirks” saving that vi back to 7.0 for you, but I believe I got everything that Chetan intended. Here it is.
Hope that helps,

-GDE

[jc288]

Thanks. I'll give it a shot.

[jc288]

I am having trouble with the timing of the data acquisition. The program is running fine and reading the data quite well, but I cannot seem to get the data to come back on the graph after I hit stop. The graph seems to only capture 100 milliseconds worth of data, so when I try to compres all of the data taken, most of it is not there. I have tried adjusting the timing parameters to get the data to show up, but I am not having much luck. Any suggestions?

Thanks.

[devchander]

Amount of data diplayed on chart depends on chart history length.

and graph does not have any history memory, it just displays the data that is given as its input.

what you need to do is this. Save all your acquired data to a file ( using fule i/o functions) and use this saved data for later references

[jc288]

I am not sure how to do what you mentioned about saving the data.

I did not build the VI and I am unsure of where I should place the 'write lvm file' command in the vI

please help.

thanks.