input generated continuos wave and shift its phase

[ethen99]

Thanks yes I wanted convert dynamic data to waveform data tyoe but I still cant get what I need

is there a way to output 3 generated continious waveform in labview...on elvis ii board only 2 analouge outputs are providd.ao0 and ao1 but I need 3

[tbob]

I'm not familiar with elvis ii board.  But it sounds like it won't do what you want it to do, produce three signals.  Also, you would do better to forget DAQ Assistant and all those express VIs and learn the real DAQmx discrete functions.  They give you more flexability and they don't use that stupid dynamic data type.  They use waveforms and DBLs directly.

[ethen99]

I have to make a 3 phase star connected circuit and as u know i need 3 sine wave with 120 phase shift to build this circuit..first I started with labview but as I said it is only possible to generate 2 waves because 2 analoge output are provided on ELVIS ..then I tryed to get the other signal from a real function generator and the other 2 from Labview but it didnt work because in a 3 phase circuit except phase everything of 3 signals should be the same..better to say it is not possible to use 2 different wave generators....then I decided to input the signal from a real function generator ...shift its phase and then output it again to have 3 signals from the same generator..this time I faced another problem..thanks to your help and CJHartshorne I could shift the signal but the problem is as u seen the signal is incomplete.in your sample u have used sine waveform.vi and we sill have this problem

I really dont know what to do.if there was 3 output on ELVIS board to problem could be solved as easy as possible

[tbob]

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@ethen99 wrote:

I have to make a 3 phase star connected circuit

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What is a star connected circuit.  I have heard of 3 phase Delta and 3 phase Wye, but never 3 phase star.  However, you are right in that it must be the same sine wave with all three being 120 deg apart.

Could you not generate all three phases from Labview:

[ethen99]

 Wye also called Star connected.

This is an exercise and this exercise conisist of 2 parts.simulation and build the real circuit.I have done the simulation part in Labview as u did but for the second part the circuit should be build on ELVIS and the students should use real resistors and inductors

[johnsold]

Read the instructions for your exercise closely.  If the hardware device you are using does not have three analog outputs, it is unlikely that the instructions actually specify that you must generate three signals that way.

Think about what you are actually asked to do and not what you think is the easy thing to do.

How about three digital outputs and low pass filters?  How about generating the third phase from the first (or the first two) and some phase shift circuits?  Scott-T transformer connection?

Lynn

[tbob]

So you have to take a sample from the real generator and shift it by 120 and 280?  Look at the attached vi (LV2009).  Replace the sine wave generator with the DAQ waveform obtained from your real signal generator.  I hope this works.

This will only work if you capture a complete set of cycles, i.e., not ending the input waveform in the middle of a cycle.

[ethen99]

@johnsold

u are right .it is possible to shift one signal by shift circuit but this experiment is designed for first year students and this circuit is a bit difficult for them

thob

many thanks for the attached vi.I will try it tomorrow .just would u please help me what DAQmx frunctions I can use to read  and sample the generated wave instead of using the express one

[tbob]

I'll be glad to help.  But you should study the NI examples to start.  Look for Find Examples under the Help menu.  Search for DAQmx.  There are a bunch of examples.  Look for a description that fits your needs.  You can start with the example vi and modify it to your needs.

I'm glad to hear that you want to take a step in the right direction, away from Express VIs and using the real thing, DAQmx discrete functions.  Now you are becoming a real LV programmer.

[ethen99]

Hi thob.I have attached 2 files ..still non of the working.. I can get the signal but the phase shift between them still vary and because of this line to line voltage is not constant.