LabVIEW
clearing waveforms
Hi Jason, Thank you for your help. I am a complete newbie to labview this is my third day using it. I tried using the value property and wiring a constant and still does not work it gives me run errors. Would you mind if you can do it for me so I could learn, in addition to the timing delay you mentioned (so as not to hog up the processor), as It would be a great oppurtunity for me to learn. About the hidden block diagrams, I did not spot any?
Best
Alloush
I am sorry Alloush. I am a firm believer in learning by doing. 
You are doing really well for your third day, I must say. I will walk you through what I did.
First go to the block diagram. Right click on the Measurement indicator and select Create>Property Node>Value.
Drag the created node off to the side and switch over to the Clear case. Drag the property node into the cleare case. Right click on it and select Change to Write. This will allow us to write whatever you want to the graph. Since we want nothing (i.e. default data), we can right click on the input terminal and select Create>Constant.
The wait is pretty simple. You can find it on the Timing palette. Without the Wait, the vi will attempt to process the Initialize case over and over as fast as it can. 1ms is enough of a break to free up the processor for other tasks, while short enough to prevent the bizzare case of someone pressing two buttons at the same time.
Finally, if you grab the case structure and drag it down a couple inches, you will see that the stop condition for the while loop is hiding back there.
You are doing really well for your third day, I must say. I will walk you through what I did.First go to the block diagram. Right click on the Measurement indicator and select Create>Property Node>Value.
Drag the created node off to the side and switch over to the Clear case. Drag the property node into the cleare case. Right click on it and select Change to Write. This will allow us to write whatever you want to the graph. Since we want nothing (i.e. default data), we can right click on the input terminal and select Create>Constant.
The wait is pretty simple. You can find it on the Timing palette. Without the Wait, the vi will attempt to process the Initialize case over and over as fast as it can. 1ms is enough of a break to free up the processor for other tasks, while short enough to prevent the bizzare case of someone pressing two buttons at the same time.
Finally, if you grab the case structure and drag it down a couple inches, you will see that the stop condition for the while loop is hiding back there.
Message Edited by jasonhill on 08-15-2006 09:41 AM
Message Edited by jasonhill on 08-15-2006 09:42 AM
Message Edited by jasonhill on 08-15-2006 09:44 AM
Message Edited by jasonhill on 08-15-2006 09:44 AM
Curious. I am not sure why clear is not working as expected.
As for saving? I like using Write Waveforms to File. Where to put it? If you want to save it every time it is run, just stick it in after the aquisition loop closes.
If you only want to save sometimes, you need to be a little more sneaky. You will need a shift register. It would be worthwhile to pull up the help file on this one, its pretty good. It is a little involved to describe all the steps (even with illustrations) So I broke down and included an example. I put a save in each location described. Delete the one you do not plan on using. I did not add a save button (yet). That will need to be lumped into the array in the initialize case.
Note that each case passes the waveform wire through. This is because each case must have some value for the waveform array, but only the run and clear cases actually change anything. I also changed up the method for clearing the array. I explicitly destroy the Y-values for each waveform. I do not have any DAQmx hardware on this machine, so I cannot test it. But it should properly clear the array, now.
In hindsight, I could have just deleted all that junk in the clear case for clearing the waveforms and set the output terminal to "Use Default if Unwired" like I described in the first post.
Try this if it is still not clearing properly.
As for saving? I like using Write Waveforms to File. Where to put it? If you want to save it every time it is run, just stick it in after the aquisition loop closes.
If you only want to save sometimes, you need to be a little more sneaky. You will need a shift register. It would be worthwhile to pull up the help file on this one, its pretty good. It is a little involved to describe all the steps (even with illustrations) So I broke down and included an example.
I put a save in each location described. Delete the one you do not plan on using. I did not add a save button (yet). That will need to be lumped into the array in the initialize case.Note that each case passes the waveform wire through. This is because each case must have some value for the waveform array, but only the run and clear cases actually change anything. I also changed up the method for clearing the array. I explicitly destroy the Y-values for each waveform. I do not have any DAQmx hardware on this machine, so I cannot test it. But it should properly clear the array, now.
In hindsight, I could have just deleted all that junk in the clear case for clearing the waveforms and set the output terminal to "Use Default if Unwired" like I described in the first post.
Try this if it is still not clearing properly.Message Edited by jasonhill on 08-15-2006 10:32 AM
