Scan rate and samples for FFT affecting dt

Question

Hi,
I currently acquire data from an accelerometer and set the scan rate of the clock to 5120 S/s. I then use the Analog 1d Wfm Nchan N Samp to acquire 5120 samples and then use FFT analysis on it to create a frequency chart. This gives me a dt of 1 i.e. a resolution of 1Hz.
The question i have is how can i sample the data with a dt of 1 at a faster rate.
For example i change the scan rate to 10240 and still aquire the samples at 5120, this allows me to sample twice a second but gives me a dt of 2 (2 hz resolution) when i do my FFT analysis. All that happens by upping the scan rate for the sample clock is that i can now detect peaks at higher frequencies.
By this i mean if i just scan at 5120 S/s using my card , when i do the FFT it goes upto 1100Hz approx , if i double the scan rate, it then doubles this to 2200Hz approx, but then reduces the resolution
How can I improve the update speed and still keep a DT of 1?
Thanks
Mike
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Answer 1

Hi,
Unfortunately i dont think i am quite making clear what i mean
Apologies so I'll try again..... 
   If I aquire the data at 5600S/s and my number of samples is also 5600. When i do the FFT peak spectrol measurements my df would then be equal to 1. By this as i understand it, it means i have a resolution of 1Hz on my FFT graph/data.
This is all fine, but if i want to update the graph or indeed save the data to disk at say 5Hz how do i do this and still keep the resolution of the FFT at 1Hz??.
If i change the S/s for the clock, all this does is increase the frequency range it does its aquiring over in the FFT. i.e. if its 5600 S/s my FFT goes upto 2550Hz on its X axis. If i up it to 10200 S/s my FFT goes upto 5100Hz on its X-Axis.
Therefore if i keep the same samples in my aquiring waveform i would get it to run at twice a second if my sampling rate was 10200 and my samples were 5100, BUT my resolution would go down to 2 on the FFT chart.
How can i sample at a faster rate at the frequencies i want yet still keep the reolution to 1 on the FFT?, i almost want to set the sampling rate per 10th of a second i suppose to enable me to update at a faster rate but this isn't possible - is it?
  Many thanks
  Mike