A/D programming

[JohnGalt]

I have searched through the forums and found all of the entries to specific to be of any help. I just want to know how to do basic A/D communication. I was told I have some devices I need to add to a program that can only communicate through A/D, but I can't find anything about how to do this in any of the manuals, and I believe trying to figure it out on my own would only result in headaches. Therefore, I ask for help from you guys, because you all know a lot more about this than I do.

Thank you,
Cole

[Dennis_Knutson]

A/D communication with what specifically? One type of A/D conversion is done with a data acquisition board that you add to the computer but it could also mean a stand-alone instrument. Outside of the sound card, there is nothing built-in to a computer that will do A/D conversion. LabVIEW will communicate to devices that will do this but you have to pick and buy the specific hardware. You need to know the type of signal you want to digitize. Is it voltage, current, frequency, temperature, vibration, etc.

[JohnGalt]

I will be communicating with a Brand Gauss Rackmount Temperature Controller. It will change from Thermocouple to A/D (I already know how to do this) and read a voltage. I have the DAQ card and will be ordering the conversion devices that will read a certain, not yet decided, amount of voltage per degree. All I need to know is what Labview Function to use to get this voltage.

Thanks.

[Dennis_Knutson]

Assuming you'll be using the latest DAQmx, open the NI Example Finder from the Help menu. On the Browse tab, expand Hardware Input and Output>DAQmx>Analog Measurements. There are subsections for reading voltages and reading temperature. You should also read the LabVIEW Measurements Manual that is part of the LabVIEW Bookshelf also from the Help menu.

[tbob]

Usually, a voltage signal is wired into an analog input of a DAQ card.  The maker of the DAQ board must supply the Labview drivers in order for Labview to communicate with the DAQ board.  In the case of an NI DAQ board, the DAQ functions come with Labview.  The functions basically allow you to configure the DAQ, read analog input values and write values to cause analog outputs.  If you specify which DAQ board you are using, you will get better help.

[JohnGalt]

The board is a Meilhaus of some kind. Will get more detail when I go to the lab later today. But it should have come with drivers. It came with a whole CD that I installed so it should work. BTW, about the DAQ thing. Is that using the DAQ Assistant, because I have tried using that and it never really worked very well. Will check out the sample program you mentioned.

[Dennis_Knutson]

Don't assume anything with a non-NI data acquisition board. If it doesn't come with a LabVIEW driver, then you may have to write your own. If all that is has is a DLL, then you need the details on it and can use the Call Library Function. The DAQ functions (DAQmx, traditional DAQ, and the DAQ Assistant) on the LabVIEW palette are only for NI DAQ boards.

[JohnGalt]

The board is a  Meilhaus ME-4670i. I will look online for some specifically Labview drivers. They should be out there somewhere. What is a DLL, and how do Iuse the Call Library Function. I have clicked that button on the palatte and it comes up blank. Is there another thing I have to do first?

Thanks again,
Cole

[tbob]

After you put the Call Library Node on your block diagram, double click on it.  This will bring up a Call Library Function Window.  Here you can put in the DLL name, function name, and parameters.  You need to know the function name and parameter types in advance.

[JohnGalt]

OK. I found drivers on the CD, but I don't know how to use them. But anyway, I shall try what you said tbob, however, how do I find the DLL name, function name, and parameters? Would they be in manuals of the various devices I will be communicating with?