DAQMx Write und read function

[nichts]

Hello,

I want to use DAQMx functions for my projekt.. but I do not understand one thing. Wenn I have a differnet Input should I use DAQmx write  and for the Output DAQMX Read? or better said what is the different betwen DAQmx write and Read, When I can used write and read? 

[Dennis_Knutson]

Pretty simple, actually. If you want to output a signal from the DAQ device to something external, you use a DAQmx Write. If you want to input an external signal into the device and pc, you use a DAQmx Read.

[Stephan_D]

Hi nichts,

use the DAQmx read function, if you want to acquire a signal from your card. If you use a differential input, you also use the same vi (DAQmx read) and change the "input terminal configuration" on the DAQmx Create virtual channel vi to differential mode.

If you want to generate data from your PC and output those data over your DAQ-Card, use the DAQmx write VI.

If you use the DAQmx driver the first time, I would recommend you the following internet page:

Learn 10 Functions in NI-DAQmx and Handle 80 Percent of Your Data Acquisition Applications - Developer Zone - National Instruments
http://www.ni.com/white-paper/2835/en

You will find all necessary information about the important part of the DAQmx driver on this page.

[nichts]

Hello 

Thank you for the answer.Yes, It is my first time, that I work with DAQ.

I write know my read.vi and I want to programmer the Write.vi but I have other question. In read function I greate virtuell channel and changed to differential mode becuase I have it a different Input from different Devices  but now I want to  transfer the Signal from my DAQ card to the PC, so my question is,  should I greate a virtuell Channel in the write.vi too, if yes, I think I have to change to channel to one channel for each device??  ? and how I can connected the read.vi and write.vi together?  should I programm a 3rd. VI  I do not have any Idea? 

BR

[Stephan_D]

Maybe you should post the programm code in a first step

[nichts]

I will do it  tomorrow because, I do not have it now in this pc, only in the university pc. I do not have labview here.. 😞

[nichts]

hello Stephan_d,

my Programm looks as the attached photo.. becuase i have tow card 

[Dennis_Knutson]

That image is unreadable. Post the actual VI. And what do you mean by multiple devices? Different sensors to a single data acquisition card will use a single DAQmx Read. And different sensors does not at all correlate to using differential mode. It is the type of sensor and the electrical connection that determines differential or single ended.

[nichts]

I connected two  DAQmx card  together, because each DAQ has only 16 Input and i want connected 31 device to one pc and measure the value, so i have here master and slave device .Therefor i used two DAQmx Read .. -Sorry that i can not add the vi.. because, i do not have a labview here and the the vi in other place