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How can I scale a graph for frequency instead of time or number of points?

Hi All - I have an application where I am reading the trace of a carrier from a spectrum analyzer. I have graphed this in the past with reading points on the trace which give me frequency and power. However that is very slow compared to just reading the trace off the analyzer which is returned as an array of 1001 power points in dBm. Because it is returned in dBm the Y scale of the graph is fine. However the X scale reads from 0 to 1000 which are he numvber of points. Is there a way to change the X scale or reflect the frequency of the data? For example I have the center frequency and the span setting from the analyzer and from that I can determine the start and stop frequency. However when I apply the minimum and maximum ranges for the X scale the displayed result changes. I would just like a way to change the X scale to what I want w/o the display being affected. Is this possible? Is there another solution that does not use the standard graphs in Labview that makes this possible? Thanks in advance for any help.

 

Troy

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If you just got an array of values, you can use the property nodes XScale.multipier and XScale.Offset to scale your graph.

Your multiplier usually is the frequency bin distance (1/capture-length or here the span/1000) , and offset mostly zero (if your first bin represents the DC part of the DFT, here center -span/2)

Have you searched the NI drivers if you get a ready made driver of your SA? Some already read the frequency domain plots as a waveform including all scaling ...

 

Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

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