Number of samples and rate

[*Antares*]

Hi,

I am acquiring data from a triaxial accelerometer (so 3 channels: X,Y,Z axis). 

So far I wrote a very simple code using DAQ Assistant:

I am acquiring using "N samples" acquisition mode but I don't understand the relationship between number of samples (Ns) and rate...

I mean Ns is how many samples I want in a single acquisition while the second is how often a sample is taken. 

I ran the code using as an example Ns=1000; rate=1000Hz and print data as time series.  I would expect to have 1000 samples in 1 second (time=Ns/rate) instead I have 1000 samples in 0.6s.

Or again I tried with Ns=1000; rate=100Hz with an expected time of 10s instead it is 0.6s again.

I don't understand the relationship between the two values

[GerdW · Accepted solution]

Hi Antares,

which device are you using?

What does its manual say about possible sample rates?

Did you check the actual samplerate of your acquired signal?

(I guess it's one of those devices with very limited sample rates. When 1000 samples are acquired within ~0.6s then the sample rate is ~1.65kHz, which is used as minimum samplerate of DAQ devices like NI9234.)

[*Antares*]

Yes it is a NI9234.

Ah ok I didn't consider that!

The possible sampling rates are calculated as fs=(13.1072MHz)/(256*n) where n=1,...31. 

Thank you! 

[GerdW]

Hi Antares,

RTFM: Read the fine manual!

😄