How do I time my 'write to file'? Difficulty: Complete Newb

[becktho]

Ralph:

Then you have just to compare the measured values in a second case-structure which is parallel to the other.

Jason:

Appending the signals results again in huge files. As far as I understood Ralph just wants to write one measurement every 60seconds and the other measurements are just to trigger an analog output.

Thomas

[Ralph@NES]

Perhaps I'm being a bit vague.  I don't need to write accumulated data once a minute, just a snapshot once a minute.  The 'save data' function only needs to pull that one sample at that second and wait a minute before it goes again.

EDIT:  Yup, that's what I'm trying to do.  Small file of general representative temps but constant monitoring for shutdown.  Thanks.

Message Edited by Ralph@NES on 05-12-2006 09:01 AM

[Ralph@NES]

"Then you have just to compare the measured values in a second case-structure which is parallel to the other."

Once again to emphasize my newbness and general ignorance, I have no idea what you mean by that.

So far the modified VI seems to be working.  It's writing data every 60 seconds and seems to be constantly monitoring.

[jasonhill]

I'm sure becktho has a more elegant solution, but this is how I would do it:  Convert the signals to a 1D array of scalars and compair them to your shutoff temperature. If any one of them is above the shutoff, kill the loop.  I think the DAQ Assitant is bright enough to close itself properly when the loop ends, rather than requiring its own stop signal.

Message Edited by jasonhill on 05-12-2006 09:16 AM

[Ralph@NES]

That seems simple enough.

However, I'm less concerned with killing the loop than with triggering my analog output to shut off a physical relay attached to our test rigs.  I need it to see 250+ degrees and signal that analog output.

[jasonhill]

Well, you could add a second case structure between the OR Array Elements and the Stop.  Create a second DAQ Assistant that sends the 5V to the relay and put that in the "true" case.  Or you could exploit LabView's dataflow paradigm.  Put DAQ assistant2 outside the while loop.  How do you make sure the loop executes first?  You could use a wire, but the loop does not produce any data that the DAQ Asisstant2 requires.  How about the error out from the first DAQ Assistant?  Like this:



For bonus points, I included a little logic to record the very last data set.  This captures the failure timestamp and gives you and idea which sensor(s) saw the overtemperature.

Message Edited by jasonhill on 05-12-2006 10:46 AM

[Ralph@NES]

Now that's cool.

[Ralph@NES]

Now I just have to figure out Analog Output.

I've got an SCXI 1102/b/c with a 1303 terminal block on it.  Are the ones labeled 'out0' etc going to be my connection?

[Ralph@NES]

And if I'm understanding this right, the error out from my DAQ asst one will occur when the value exceeds the range I put in for my 'input range' for the thermocouples, correct? 

I'm assuming that when it triggers the 'error out' to the 2nd DAQ asst, all I have to do is have it configured to send a single 5v sample for my relay trigger and I'm done?

[jasonhill]

I am not familiar with your hardware.  If no one else speeks up, you may try looking in the hardware forum.

The error out is a special type of cluster: a boolean (is there an error?), a 32 bit INT (the code for the error), and a string (error source).  DAQ Assistant will return the error cluster after it finishes the aquisition, even if it does not encounter an error.  In most cases, the error cluster can be used to prevent "down stream" code for executing when there is some kind of problem earlier in the program.  In this instance, I am using the error wire more for flow control than anything else.

Just set up the second DAQ Assistant to sent the 5V signal.  It will execute when there is data in all of its wired inputs.  In this case the only wired input is the error cluster and it is "filled" when the loop stops.

Message Edited by jasonhill on 05-12-2006 12:09 PM