how to enhance frequency resolution of fft spectrum on x-axis

[tronoh]

Dear Sir

I get the frequency spectrum of my real time signal. Frequency span that I want to analyze is 0~500hz. I get that span by setting the sampling rate. But the frequency resolution coming on graph is of 100hz (as shown in attachment). My requirement is to have frequency resolution of 10hz with same frequency span. Please guide me how can I achieve this.

I shall be thankful to you

Kind Regards

Muhammad Irfan

Student

UTP Malaysia

0060149087570

[Dennis_Knutson]

As noted in the thread you hijacked, increase the number of points.

[tronoh]

I set the dt value to 0.002. For this I set sampling rate 2000hz and no.of samples 1000000. In this way I achieve frequency span of 250hz. But resolution is still 100hz (as shown in attach 1). My question is how can I set resolution to 10hz? I increase the number of samples but from doing this only the frequency span changes and resolution remain same as 100hz. Resolution become 10hz only when I set total frequency span to 50 hz (but My frequency span of intrest is 0~500hz or 0~250hz not below thos).

I am attaching the gaph in attachment 2 from where you can undersatnd what type of resolution and frequency span I want.

[RavensFan]

All of your pictures show a much finer resolution than 10 Hz.

Are you actually talking about the grid spacing of your graphs?

[tronoh]

Yes I am talking about the grid spacing. I want to have grid spacing of 10hz

[RavensFan]

Then you need to set the markers for the X-scale.

 

[tronoh]

Dear Sir

I try to do same as per your instruction but can not get required result. I attach the my program. Please comment on it that where is the mistake.

I shall be very thankful to you

Kind Regards

Muhammad Irfan

[RavensFan]

Mine is ramp by delta, while yours is ramp by samples.

There is no need to put that in the loop.  Since they never change, they only need to be set once outside the loop.

[tronoh]

I shift it outside the loop. But still same situation. How to convert ramp by sample to ramp by delta?

[RavensFan · Accepted solution]

Click on the polymorphic selector that is below the subVI and choose Ramp by Delta.