Signal Generators

Showing results for 
Search instead for 
Did you mean: 
Reply

how to make bode plots in Labview 7.1 without using Control Toolbox

Re: how to make bode plots in Labview 7.1 without using Control Toolbox

I am using Labview 10. I have connected a signal generator, a LP RC filter and an oscilloscope. I am using Labview in order to control the generator (sine with frequency sweep) and acquire the signal from the scope. I want to plot the Bode diagram without using the transfer function, from the amplitude of the sine signal and the frequency.  

 

Thank you very much.

Best Regards.

0 Kudos
Message 11 of 17 (3,652 Views)
Reply
0 Kudos
Highlighted

Re: how to make bode plots in Labview 7.1 without using Control Toolbox

Hi pflo,

Are you using the CD Bode Plot VI or the SI Bode Plot VI?  For the CD plot you must use a transfer function.  Below, please find a link to an example on how to create a Bode plot without using the toolkit.  


Regards,
Kira T
0 Kudos
Message 12 of 17 (3,615 Views)
Reply
0 Kudos

Re: how to make bode plots in Labview 7.1 without using Control Toolbox

Hello there! I was looking around the net to get some informations or suggestions on how to get the bode plot from the response of an electrical circuit (for example a LP filter) feeded by a sine-sweept signal.
The sine-sweep is generated by a function generator, therefore with an oscilloscope I acquire the response of the electrical circuit that is " sent " (with IEE488 bus) to LabView.I have solved the problem of acquiring the output of the circuit , but I don't know how i can plot Bode.

 

I wouLdn't use a pre-existing subVI..thanks for the attention and sorry for my bad english.

0 Kudos
Message 13 of 17 (2,595 Views)
Reply
0 Kudos

Re: how to make bode plots in Labview 7.1 without using Control Toolbox

Hello Caster,

 

I am wondering in what data type you have the information on LabVIEW of the response of the electrical circuit.  Please review this information on frequency response.

 

http://www.ni.com/example/6450/en/

 

Please reply with your insight on this matter, and maybe what is your final goal on this project.

 

 

Regards,

 

David M.

National Instruments 

 

 

Message 14 of 17 (2,578 Views)

Re: how to make bode plots in Labview 7.1 without using Control Toolbox

Thanks for the attention Dado.MB.
I've read the documentation suggested, but,  excepet the first paragraph (frequency response), the rest is focused on the CD Bode VI.
My final  goal is to plot the bode diagrams using the information obtained by, allow the term,  "temporal response"  of the electrical circuit  acquired by the oscilloscope.
In input, I feed the circuit with a sine-sweep signal generated by an external  function generator.
I thought I'd take the peaks , using the subVI "peak detector", and the instants of time associated  to build the magnitude bode diagram (because of the frequency vary linearly during the sweep time, by a simple equation I can obtain the desired frequency in relation to the instant time considered).

I will have a couples of values (magnitude;frequency) for each peak detected..then with these values I might be able to draw the  magnitude bode diagram.

It may be a plausible idea?

The data acquired by the oscilloscope are converted into 16bit integer.
I continue to say sorry for my bad english..

Message 15 of 17 (2,566 Views)

Re: how to make bode plots in Labview 7.1 without using Control Toolbox

[ Edited ]

Sounds like you were having some trouble back then... 

 

The Bode diagram is just a NORMAL XYGraph adjusted to plot a curve on a log(10) scale..... yo DO NOT need the control module to build your own for a case as simple as this... all you need to do is simulate the transfer function from (let´s say) 0 to 100Khz.. and plot the results...

 

I´m attaching my "low pass active filter" simulation, along with the bode plot for that specific function.

Note one part of the SubVI is calculating Vout and the FOR loop is iterating to give 100k values of X to the transfer function..

 

Not very complicated huh?

 

Its in spanish...  you will understand.. (At least is not german or russian) hahahahaha

 

No disrespect to NI or the moderators, but no student is going to pay 3000 USD over a weekend project for an electronics class... so "suggesting" getting the module is not a very wise advise in this case

0 Kudos
Message 16 of 17 (1,276 Views)
Reply
0 Kudos

Re: how to make bode plots in Labview 7.1 without using Control Toolbox

[ Edited ]

.

0 Kudos
Message 17 of 17 (1,268 Views)
Reply
0 Kudos