DAQ assistant is not recording data when case structure is false

[tousif54]

yes. I'm 100% certain that it's taking longer than 15 minutes. Look at the image I've attached. Instead of 90 minutes the experiment took 110 minutes to complete. Does it convince you now? And, no did not try with 5 min interval...

[RavensFan]

That's thermal response, not directly how long is the relay on.

If you heat up an oven then turn it off, the oven is going to stay hot longer.

Since you are the one with hardware, you'll need to debug/troubleshoot this yourself.  Like I said, put in a feature that will log the time that the output changes from true to false and false to true.

[tousif54]

Again, once the heater (relay) is off there is no reason why the temperarue will go up. I know very well that it takes certain amount of time to cool off any body due to the thermal mass of the system. But as I said, if the relay as well as the heater would turn off right at 15 minutes, you would see the sudden temperature reduction happening right at the black vertical line. Thanks.

[crossrulz]

I have to ask again, where is this being measured from?  Outside measurement?  DAQ in this VI?

[tousif54]

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@crossrulz wrote:

I have to ask again, where is this being measured from?  Outside measurement?  DAQ in this VI?

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Yeap. The DAQ Assistant. It is recording the thermocouple data.

[RavensFan]

So have you tried debugging the LabVIEW code to timestamp when the relays are on and when they are off?

[tousif54]

I'm not actually that good in LabVIEW.  Don't even know how to do that.  Sorry.

[RavensFan]

Then sit next to the system and listen to the relays click and compare to the time on your watch.

To do it in LabVIEW, there is a function called boolean crossing point by point.  Feed the boolean signal into that, and that into a case structure.  It will trigger a true whenever the state of the boolean changes.  Inside the true case, have the current time get written to a file.

[tousif54]

Sitting next to the system would be easier. 

[crossrulz]

Even easier would be to add an analog line to the DAQ Assistant to sense the relay control signal.  This would require a little bit of electrical work (one wire could do it).