MyDAQ

[Wuffi]

Hello everybody out there using LabVIEW,

Performing a single measurement with the NI myDAQ using a custom LabVIEW VI works fine.

Having seen an example of measuring the temperature via thermistor connected to myDAQ's DMM (see http://www.ni.com/example/31408/en/), I wanted to do the same.

However, setting the measurement period for myDAQ's DMM in a custom LabVIEW VI to contiuous would result in an error message. In the example of the thermistor, this is done via a while-loop, which seems to be more cumbersome to me.

Why is it not possible to continously sample the voltage/current with the DMM? Is this something one would do with the analog input channels? Why is this not done in the thermistor example?

These might be trivial questions for an expert, but I am just starting to use LabVIEW and don't have any experience with it yet.

Kind regards

[JGoebel]

Hi Wuffi,

what kind of error message do you recieve when setting the DMM Task to continuous? I think the DMM doesnt support a continuous measurement mode. Continuous means Hardware-timed (opposite of "on demand"), so the hardware needs to be able to generate its own clock for the measurement. I think the myDAQ does not support this for the DMM. But you can still do an acquisition "on demand" as in your example. For temperature there should be no reason for a hardware-timed acquisition. "On demand" is basically also a continuous acquisition since you can demand samples over and over.

Hope this helps, let me know if you have further questions.

Best,
Jan Göbel

Staff Applications Engineer

National Instruments

[Wuffi]

Thanks a lot for your help.

As far as I had understood, the analog inputs of the myDAQ can be used hardware-timed (allowing for continuous measurement), but the DMM doesn't. Therefore, I was surprised to see the "myTemp" example, where the DMM was used to monitor ambient temperature.

I was hesitant to use the on demand measurement, but it sounds exactly like what I was looking for.

I'll try to find this option in the DAQ assistant, which I use in my VI.

It might be helpful, if some information could be added to the temperature example.

It shows the Front Panel, but not the configuration of the DAQ assistant within it, which makes it hard to follow for beginners like me.

[JGoebel · Accepted solution]

Hi Wuffi,

are you talking about this tutorial? http://www.ni.com/example/31408/en/

Because it does have the configuration of the DAQ Assistant.

Still I think that on-demand is the correct and easiest way, since temperature doesnt need a super exact sampling rate usually.

Let me know if you have further questions.

Best,
Jan Göbel

Staff Applications Engineer

National Instruments

[Wuffi]

Thanks a lot for your reply.

I totally agree that there's no need for exact sampling for the temperature.

The linked tutorial was exactly what I was thinking about. My problem with the configuration is, that it just shows 1 tab and not the others. If I set the configureation like it is done in the image, I just get 1 single numerical value, that I can display in a numerical field, but it is not accepted for plotting (which probably wouldn't make sense for a single value).

[JGoebel · Accepted solution]

Hi Wuffi,

ah thats what you mean, I think the other tabs are just left as they are, at least thats my guess, since its a pretty simple example without any advanced features.

Best,
Jan Göbel

Staff Applications Engineer

National Instruments

[Wuffi]

Thanks again. Everything is up and working now.

I would accept it as a solution, but there doesn't seem to be an option for this in the forum here.

[JGoebel]

There should be an option to "set as solution", but don't worry about that. Its less a solution than just telling you what you already knew on your own 😉

Best,

Jan Göbel

Staff Application Engineer

National Instruments