Single-point data filtration

[peldao]

Hello, i am trying filtrate voltage data from single point task, but there is a frequency error... I have sampling frequency set to 120Hz and i want bandpass filter for example 30-40Hz...  

So where is problem? I tried use timed loop or "align and resample" to make sampling frequency, but this filter still does not work...

Do you know, how use this filter with single point task? When i make my own FIR filter with same settings, results are not same, so that is reason why i want use this filter.

If i use DAQ Assistant, there are no errors, but i cannot use it for other reasons (1)i cannot use single point and daq assistant together, 2) daq assistant doesn't know to get pressure)

[Dennis_Knutson]

There is no sample frequency when you do a single point acquisition. Use the pt-by-pt function if you don't want to acquire multiple points in your acquisition. Why you don't want to acquire multiple points is not at all clear. Why you don't use the regular DAQmx functions is also unclear. The use of the timed loop on anything other than real-time LabVIEW is not worth it.

[natasftw]

Showing us express VIs isn't very helpful.  You're forcing us to guess what your settings are.  What are your settings inside the filter VI?

[natasftw]

---

@Dennis_Knutson wrote:
The use of the timed loop on anything other than real-time LabVIEW is not worth it.

---

It's incredibly powerful in FPGA as well.  But, there's no real reason for it in regular LabVIEW

[Dennis_Knutson]

Yes, I should have been clearer.

[peldao]

I have voltage and pressure acquisition by single point with120 samples per second. Isnt it 120Hz? In my opinion timed loop can set 120 hz too.

I am using fir windowed filter, with same settings like express filter, but output is different. Thats reason why i want use express filter.

What do you suggest to use to acquire both signals with using express filter, which need input signal with sampling frequency? 

[Dennis_Knutson · Accepted solution]

Those images add nothing to the discussion. If you are acquiring a single point at a time, you have NO frequency and cannot use the normal filter function. Do what I said or use multi-sample read or single point read and build array before doing a filter. Best is to use the daq with multiple samples.

[peldao]

I followed your advice and used pt-by-pt filter. Thank you very much.