Standing Waves

[suvi90]

How can i generate Standing sine waves ? As input i have three parameters

1.Frequency

2.Amplitude

3. Phase

I have to generate 8 sine waves.

[P@Anand]

What do you mean by standing sine wave?

Did you check the functions available in LabVIEW?. Try the following example.

 

[Rob65]

Use a for loop to fill an array with values ?

This will then generate an array with a (fixed) number of values representing your sine wave.

Different frequency, amplitude and phase is just a matter of performing the correct calculations.

I'm assuming that with 'standing wave' you are referring to a fixed array with a number of samples that don't change (in contrast to a running wave that defines a sample at each time interval while running).

With an "In Place Element Structure" you can use "Array Index / Replace Elements" to change elements of an existing array or you can use a shift register to loop an array back into the loop and add elements.

LabVIEW comes with a number of examples of how to use a waveform graph or chart - that could also get you in the right direction.

Rob

[suvi90]

Hi

Thanks for the reply. This is my VI for sine generation. Can You suggest how to generate a Standing Wave from this idea. The "Sinus Signale" is again converted into waveform.

[johnsold]

You still have not told us what you mean by a "standing wave." Typically a standing wave is a pattern of voltages on an transmission line or of amplitudes of liquid surfaces along a channel.  You have not described anything like that.

Please show us what the eight sine waves should look like and what the standing wave should look like.  If you cannot make your LabVIEW program do what you want, create an image in a graphics program and post a .png or .pdf file (no bitmaps).

Lynn

[MoReese]

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@johnsold wrote:

You still have not told us what you mean by a "standing wave." Typically a standing wave is a pattern of voltages on an transmission line or of amplitudes of liquid surfaces along a channel.  You have not described anythinIt that.

Please show us what the eight sine waves should look like and what the standing wave should look like.  If you cannot make your LabVIEW program do what you want, create an image in a graphics program and post a .png or .pdf file (no bitmaps).

Lynn

---

It's a physics term meaning the waves do not propagate, but are stationary (this is a very basic definition but standing waves can be caused by two opposing waves traveling in opposite directions across a medium).  What is the purpose of generating a standing wave?  What are you trying to do?

[Rob65]

As Reese describes, a standing wave is a physics term. In contrast to a running wave where, when looking at one point in a medium, you see wave propagating along that point, a standing wave shows a fixed value at that point. Haven't we all done this during our first year of physics with a piece of string?

As an RF Electronics engineer I hated standing waves, all power is reflected back to the transmitter resulting in no output power and smoke ...

I interpreted this as generating an array with one (or more) sine waves but suvi90 could also mean that he wants a continuous signal at an analog output.

Rob

-- smoke is what makes electricity works, if you let the smoke out of the circuit it stops working.

[suvi90]

Hello All

Thanks alot for the inputs. By travelling Waves I meant exactly how Reese described. Here is a pic of the generated Waveform. I made the VI by getting the equation from Wikipedia

I have another question now. How can one get the last written value from a DAC card. I am using an AO card NI PCI 6713 and I want to find the last output value.

Thanks again for all you inputs.

[P@Anand]

You need to read the value where you are writing to the DAQ output so obviously you will have the latest data.

[suvi90]

Hey

If I am only using an Analog Output card with 8 outputs no Input card, then I can not read the last value.