Can I use two LabQuest express in the same Vi

[mathew_naguib]

Good Afternoon,

I am a beginner in LabVIEw for my MATLAB class. We a assigned to use LabVIEW in our final project. The project is to keep an egg warm using a fan, a ceramic heat resistor, a Digital Control Unit, a LapQuest Mini, suface probe, and temperature probe. My plan is to connect the ceramic heat resistor and the fan to the DCU unit and control it through a Digital express in LabVIEW. So we programmed the Digital Express to be dependent on the surface temperature of the egg. My problem is when I put the analog and the digital Express in the same VI it doesn't work and give me an Error. Is there a way to put 2 Expresses in the same Vi.

Here is my Vi. (The broken wire in the beginning is there because i don't have my LapQuest mini with me so there is no channel detected)

Thanks. 

[RavensFan]

What is "LabQuest"?

You mention you get an error, but yet you don't tell us what the error message says nor what the error number is.

[DuncanW.]

Hi matthew_naguib,

As RavensFan mentioned, it will be hard for us to offer advice without an error code or error message so that we know what is going wrong. If you can provide us with more information about the specific error you are experiencing, we may be able to offer advice on how to resolve similar errors.

Also, I opened your VI and it appears that you are using Express VIs drivers developed by Vernier to interface with their LabQuest hardware. Is this correct? If you are using third-party VIs, it is probably a better idea to get in touch with their support channels. National Instruments does not have documentation on these VIs and it will be hard for us to assist you in debugging problems stemming from using their code. That being said, I am happy to give it a shot if you can provide us with more information!

Best,

Duncan Waldrop

Applications Engineer

National Instruments

[mathew_naguib]

This is the error that appeared to me.

[RavensFan]

Having that error message does help.  At least it helps us know that we can't help.

As Duncan said, you'll need to contact the manufacturer or whoever provided the LabVIEW VI's to you for their support.

[DuncanW.]

Hmm that is unfortunate. The error dialog is not going to give us any information about what is going wrong in this case.

My guess is that this is an error code being generated by the Express VIs you are using from Vernier. I would double-check their documentation to see if what you are trying to do is supported by their VIs and, if that is the case, how to implement it. The forum post here supports my suspicion.

Generally speaking, when LabVIEW throws errors like this one it is because an error was generated by something other than LabVIEW and LabVIEW has recognized it, but cannot make sense of it as it is not native to LabVIEW. Most commonly, this can be caused by OS or third-party instruments calls failing and returning generic error codes that LabVIEW does not understand. In this case, it sounds like the drivers you are using are not designed to interface with your LabQuest device in exactly the way you have them configured.

In addition to reaching out to Vernier support, since this is a school project, it might be helpful to speak with your TA or professor about whether the LabQuest drivers support putting multiple copies of their Express VIs in a single VI. This sounds like exactly the kind of question your TA would be happy to answer at office hours! Good luck and let us know if you have any troubles with using native LabVIEW functions. We'd be happy to help there!

-Duncan

[mathew_naguib]

Thank you Duncan for your help. I figured it out by calling vernier support as you suggested thanks for the help. For the solution it was a wiring issue and the error can be avoided if you reset the device when you click the digital or analog express. Here is my final VI for people who has the same issue.