sample the signals

[Veeru]

Hi

I need to acquire a signal(through serial comms) and sample the signals.

After that i need to do FFT for original signal.pls help

Thanks

[Pnt]

You can use VISA, to read-write to a serial port. Search the Labview examples.

Labview has many mathematical functions too. Be more specific if you have a problem

[Veeru]

Thanks

I am new to LabVIEW, basically i am going to download the waveform from oscilloscope(for serial comms what are basic things i need to look at to start programming........because i got program that is not clear for me).Please help in interfacing,what are the steps i need to follow.

[Ray.R]

Start by a high level design of what you want to do.  Describe it in simple terms.  That will help you define which blocks you need to accopmplish it.  Then look for examples that fullfill those items.

Example: 

1. Acquire signal

a) Open serial port

b) Send command

c) Query port for data

d) If data is available, read it

e) Pass data to the next block

f) Determine if data reception is continuous to decide if loop is more appropriate.  And potentially have the ability of transmitting the data to another block while receiving the data.  Or data is obtained in a single shot beofre passing it for analysis / processing.

2. FFT on signal

a) Obtain data

b) Carry out FFT

c) Display / store results

In the example I described above,  you should be able to find code examples for both by doing a search on Serial Communication and FFT.  The examples will probably not interface readily to aone another, but may require a small modification.  You could establish that as your starting point.  If you are beginning to program using Labview, it would be wise to review proper coding methods (do a search). 

RayR

[Veeru]

Thanks Joe

Seems very helpful. I will have a look

[Dennis_Knutson]

And before you start writing any code, go to http://www.ni.com/devzone/idnet/ and see if there is already a driver for your scope. If you have specific questions, you need to at least provide the make and model of scope.

[Veeru]

Thanks Dennis

Manufacturer is Tektronix(oscilloscope mode: TDS430A).

There is no driver for this

[Dennis_Knutson]

No, but there is an unsupported driver for the 420 at http://sine.ni.com/apps/utf8/niid_web_display.download_page?p_id_guid=E3B19B3E91CF659CE034080020E748.... this might be a good starting point.

[Veeru]

Hi

I need to sample to analog signals

1. For example, lets the say the signals are sine and cos waveforms

2. lets consider each sampling point as theta1,theta2........, from that we can find theta,ie.. Theta=tan inverse(sin theta/cos theta)

3. After that i can plot theta with time, so for this signal i need to do FFT.

Pls help me how to sample the signals and proceed further.

[Dennis_Knutson]

Find the funciton in the manual (or in the driver for a similar scope) to download a trace. You also read the sample rate of the scope. With the trace data and sample rate, you have all of the necessary information to perform an FFT. Some FFT functions have seprate inputs for Y array and sample rate. Some have a single waveform data type as an input. You create a waveform data type with the Build Waveform function and provide it the Y array and dt.