problem with normalized frequency on fft

[r_ramirez]

Greetings

I have a problem when working with vi fft Spectral measurements, when acquiring an analog signal , the frequency of this switch to a digital frequency affected by the sampling rate, and hence the frequency axis ( of a waveform graph) gives incorrect, how can  I multiply the digital frequency by the sampling frequency to obtain the original analog frequency?

how can I save as a text file in 2 columns (frequency and magnitude in db)? I tried to write with 'WRITE measurement FILE' but  shows a header file and the columns are time and value, there is another way to store this data?

thanks

[altenbach]

It's all just data. You can easily generate a frequency column based of f0 and df and write the two colums to a plain spreadsheet file.

Can you attach a simplified version of your VI so we can better see what you are doing?

(e.g. Do you use plain arrays, waveform or dynamic data? Which fft tools are you using?).

[r_ramirez]

greetings and thanks for answering

attached the vi I'm using, the questions are 2

1. How can I multiply the frequency of the signal by the sample rate to get the right analog frequency for  example (if the sample rate is 1000 for a frequency of 60 Hz , i got  0.06 Hz observed  on the waveform graph)

2. How can I get a flat file without a statement at the top with 2 columns frequency and magnitude db

thanks

Im using labview 7.1

[Dennis_Knutson]

The Convert To Dynamic Data is incorrect. You selected to convert from 1D Array of Scalars instead of Single Waveform. Y A big clue that it's incorrect is the coercion dot on the input. You stripped all timing information so that is why the x axis is wrong.

If you want somthing simple, use the Write to Spreadsheet File.