Adding dc offset to analog signals

[Derekaka]

Hi everyone,
I am trying to generate a sine wave signal using myRIO 1900, and I have looked into the following post as a reference.
https://forums.ni.com/t5/Academic-Hardware-Products-ELVIS/frequency-matching-problem-with-myrio/td-p...

I am just wondering if I could modify the VI in order to add a DC offset to the sine signal.

[altenbach]

Yes, just use the add function and add the offset before the output. Make sure that the final max amplitude does not exceed the output range.

[Derekaka]

altenbach,

I tried adding an integer to the value after computing the sine function, but it didn't seem to work. No offset was observed in the oscilloscope.

[OA1]

Have a look at the basic function generator.

https://www.ni.com/docs/en-US/bundle/labview-api-ref/page/vi-lib/measure/masignal-llb/basic-function...

[Derekaka]

 OA1,

can it output the generated signal through the A/O pin in the myRIO?

Re: Analog Output from Basic Function Generator.vi

Someone wrote "The Basic Function Generator.vi outputs a waveform/array while the AO Write One Update.vi reads a single value so its not the right AO vi to be used for signal generation." Is that true?

[crossrulz]

You can output a waveform if you program the FPGA to do so.  Use a DMA FIFO​ to pass the points from your RT code to the FPGA and have the FPGA read this FIFO and write each point to the analog output.

[Derekaka]

Hi crossrulz,

Do I have to change anything inside the time loop except replacing the "analog out"? because I don't have any experience using FPGA. 

[Derekaka]

I am just wondering if we can add DC offset to the signals without using FPGA on myRIO.

[Henrik_Volkers]

You can always add an analog circuit to add a bias voltage ... 

(BTW: If you check with a scope, did you used DC or AC input coupling?)

If signal plus bias is within the range of the anlog output a software solution is possible.