This Document is not yet Rated

Rate this Document

Plotting in Decibels with DIAdem

Primary Software: DIAdem
Primary Software Version: 10.2
Primary Software Fixed Version: N/A
Secondary Software: N/A

Problem:
I need to configure my DIAdem report to plot data in decibels. Is there an option to automatically change the axis on the graph?

Solution:
A decibel is a dimensionless unit and, therefore, DIAdem cannot automatically infer how to plot your data in decibels unless you provide a reference. In the case of frequency versus amplitude in an FFT, you can compute the decibels by supplying a reference amplitude to the following formula (see Decibel on Wikipedia for more information):



The following steps are an addition to the FFT example that ships with DIAdem:

1. Load FFT_Expl.tdm in the DIAdem data portal.
2. Navigate to the View panel and open the Calculator on the toolbar.
3. Run the following computation:
   Ch("FFT_Result/AmplitudeDB") = 20*Lg(Ch("FFT_Result/AmplitudePeak")/.01)
   *This formula creates a new channel named "AmplitudeDB" that stores the amplitude decibel values given a reference amplitude of .01.
4. Navigate to the Report panel and open FFT_Expl.TDR. You should see the frequency plotted versus the amplitude in decibels on the y-axis.

Related Links:

Attachments:
FFT_Expl.tdmFFT_Expl.tdxFFT_Expl.TDR




Report Date: 08/24/2007
Last Updated: 08/25/2007
Document ID: 4CNDISSN

Your Feedback!	Poor  |  Excellent							Yes	No
Document Quality?							Answered Your Question?
	1	2	3	4	5
Document needs work? Please tell us why.
Please Contact NI for all product and support inquiries.