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shaker overload using daq 6211

Hi gents,

 

I'm using labview for running a shaker rig through the usb 6211.

 

I don't know why, I have a peak at the end of the signal played, which produce an overload. I use the clear task function to finish the run. Is there something else to use in order to release the signal and don't have this tick?

 

Thanks a lot, Pierre

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Hi Pierre,

 

Could you please send us some screenshots and your VI? Also what exactly is being overloaded? 

 

I hope we can get this sorted soon.

 

Thanks,

Owen.S
Applications Engineer
National Instruments
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Good morning,

 

Actually a screenshot will not be helpfull to explain that. The problem occurs at the very last input point. It looks like if the daq acquisition discharge itself. The result is then a high peak on the shaker which produce an overload (so again the overload is not due to the shaker itself but more to the program or daq discharge).

 

I enclose my program VI. The problem is maybe from my solution to clear/release the data out of the buffer/daq box..?

 

Thanks a lot, Pierre

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Good morning Pierre,

 

I've had a look at your code and I can see a few things that could be improved and may solve your problem.

 

I noticed all your code is running in parallel, is there a particular reason it needs to be?

 

You are using a load of local variables which could be replaced with either wires or shift registers if the values need to be stored.

 

Another thing I can see is you don't have a stop button for the main loop. This leads me to think you might click the abort button when stopping your code, this may not shut off or close things properly and could be another reason for your problem.

 

The last thing I can see is there is no timing in your main while loop, this can cause problems as your VI will leave no processor time to do other things.

 

My advice would be to try using a Producer/Consumer Design pattern with events. There is a Template VI which might help you to get started:

 

If you go to File > New then this box should appear:

 

Help Rig.JPG

 

Then go to the Producer/Consumer Design Pattern (Events) and a basic template is set up. Instead of continuously polling and waiting for the boolean buttons to be pressed, this design pattern does nothing until there is a user input.

 

This link may also be helpful in starting up: http://zone.ni.com/devzone/cda/tut/p/id/3023

 

Have a go at setting up this design pattern and let me know if you have any further questions or problems :). 

 

Thanks,

 

 

Owen.S
Applications Engineer
National Instruments
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Hi Pierre,

 

Just a few other things I've noticed about your VI.

 

In the case structure where you are using the DAQmx functions you are opening and closing the channel everytime you run the loop. This can lead to problems and the best way to do things is to open and close the channel outside the loop. There are lots of examples in the find examples section:

 

Help > Find Examples 

 

then on the browse tab go to: Hardware input and output > DAQmx > Analogue Measurements > Voltage > Cont Acq&Graph Voltage-Int Clk.vi

 

As an example but there are plenty more in that folder. Opening and closing the channel everytime the loop runs can be very slow and not the optimum way of doing things.

Owen.S
Applications Engineer
National Instruments
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