error on filtering ascii

[signal29]

I am having some problem on reading and processing ascii files. the problem is that when ever i try to filter this data this gives an error message that "the specification doesn't meet Nyquist criterion "

can anybody help me out that how to properly read the data and filter it and then save it as ASCII again

thanx in advance

LabVIEW Measurement

Writer_Version 2

Reader_Version 2

Separator Tab

Decimal_Separator .

Multi_Headings Yes

X_Columns Multi

Time_Pref Relative

Date 2010/08/02

Time 17:42:14.9375

***End_of_Header***

Channels 1

Samples 6328

Date 2010/08/02

Time 17:42:14.9375

X_Dimension Time

X0 0.0000000000000000E+0

Delta_X 1.000000

***End_of_Header***

X_Value signal in Comment

0.0000E+0 0.0000E+0

1.0000E+0 1.0700E+3

2.0000E+0 1.0730E+3

3.0000E+0 1.0890E+3

4.0000E+0 1.0740E+3

5.0000E+0 1.0150E+3

6.0000E+0 1.0540E+3

7.0000E+0 1.0130E+3

8.0000E+0 1.0540E+3

9.0000E+0 1.0650E+3

1.0000E+1 1.0420E+3

1.1000E+1 1.0370E+3

1.2000E+1 1.0420E+3

1.3000E+1 1.0480E+3

1.4000E+1 1.0450E+3

[RavensFan]

Your text file looks like the data was saved with a 1 Hz acquisition rate.  (The X values, are at 0, 1, 2, 3, ..... and the Delta X is listed as 1.0)

But your filter is set for a cutoff of 20 Hz.  You would need to have an acquisition rate of at least 40Hz to meet Nyquist criterion.

Either you did not acquire at the acquisition rate you thought you did, or when the data was saved to the text file, the timing information was not saved with it and it defaulted to a rate of 1 Hz.

[signal29]

the signal was sampled with 1k. actually it is a data recorded at 8kHz then i have downsampled it to 1khz. and i know the highest possible frequency content of the analog signal is 35 hz 

it may happen that time stamp is some how deleted 

but have any idea how to proceed now?

i mean to construct time stamp properly and do the filtering

[RavensFan]

You can take the waveform datatype that comes out of the Read File function.  Use Get Waveform components to get the Y array of data, then use Build Waveform to build in the correct value for dT.

You may have to do this in a For Loop with auto-indexing enabled since it is a 1-D array of waveforms coming out of the Read File function.

[signal29 · Accepted solution]

thanx thanx i am trying 

coming back in munites