LabView + NI MyDAQ

[AndreP]

Hey guys,

I have a project which requires me to:

- Build a 10k Wheatstone bridge with a thermister

- Suply 2.5V with the MyDaq to the breadboard

- Record, save and load the Voltage of the wheatstone bridge.

I opened a new project, created a VI, and opened two instances of DAQ assistance:

One to suply the 2.5V (which he doesn't let me, because I can only assign an interval of voltage, for example -2.5 to 2.5, but I would like to suply constant 2.5V), and another DAQ Assistance to make the reading of the voltage.

I connected the breadboard to the assigned ports on each DAQ Assistance, but it's still not working, I guess the problem is in the definition of the supply voltage.

I'm still also a little bit lost on how to define the range of measuring on the reader, the Wheatstone bridge have 3x 10K ohms resistors and a 10K Thermister. I used a wheatstone bridge calculator, and it gave me the output rangint from 0 to 10.000Ohms would be from -1.25V to 0.

I'm a little bit lost on how to build this project, could you give me some hints to help me build it and understand it?

Here are some screen shots:

[Bob_Schor]

You need to understand Hardware.  Do you have a volt-meter?  Do you know how to run MAX (the Measurement and Automation eXplorer)?  Try the following:

1. Open MAX.
2. Find your myDAQ (plug it in, first).
3. Open a Test Panel.
4. Choose Digital Output, and choose an Output terminal.
5. You should see that the Mode is "Voltage DC", the limits are ±10V, and it is set to output 1v.  Hook up a Voltmeter to the outputs and run the test.  You should get a 1 volt output.  How do you think you could get 2.5v?  Try it and see if it works.
6. Now set up your DAQmx Task in your code in a similar fashion.

Bob Schor

[AndreP]

Ended up powering the myDAQ with the MAX and not inside labview.

To whoever may facing some dificulties, here's the final VI:

[AndreP]

Still regarding this VI i now came across with other error:

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z0000019NSeSAM

I'm having this error, and even with that explanation and image, I couldn't implement that into my VI to solve the problem. I can't seem to conect the EOF to the Reset with the loop.

Could somebody help me please? Here are the updated VI's:

[AndreP]

Here I stry to explain a little bit better what I need:

To read the data, I created a VI with "Read File From Measurement", it's reading from LVM. And the first time I do it, it's completly fine. But, the second time, it just crashes! After a deep look at it, I learned that's what happens is that it doesn't automatically start to see from the start each time, so the first time it starts to read from position 0 to 512, and the second time he tries to start to read from position 513, which doesn't exists, and crashes!

What I wanted to happen? To restart the reading position to zero each time it reads!

The answer to the problem? Literally what is specified in this topic: https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z0000019NSeSAM

But I can't really put that to work in my VI, even with the image!