Could not get clean signal after applying bandpass filter

[Annj]

Hello,

I measure a raw PPG signal which looks like this figure below. It contains ambient noise, power line freq noise

Now, I want to filter it so that a clean PPG signal can be obtained like here.

I apply the bandpass filter as below fl:0.6Hz, and fh:2Hz at 1000Hz sampling frequency. 

However, no signal appears in the clean PPG waveform as in the picture below.

Can anyone here point out what is the possible cause? Should I change the filter type?

I attach my vi for anyone who might be interested to help me out.

Thank you.

[johnsold]

It would help a lot if you included some data.  We do not have your hardware or data sources.

Place an array indicator on the 2D array wire coming from the DAQmx Read VI. Run the VI until you have some data as shown in your images. Stop the VI. Edit >> Make Current Values Default.  Save. Then post that VI.

Also, if you can indicate what you expect the data to look like, that would be helpful as well.

Lynn

[johnsold]

The filter VIs are returning error code -20031: "The filter canot be designed with the specified input values."

The filter VIs (and others in the Signal Processing palette) return error codes but not the standard error cluster. So you need to connect those error outputs either to an indicator or use Error Cluster from Error Code.vi from the Dialog and User Interface palette.

I have not figured out which parameters are causing the error, although your filter specifications are extraordinarily tight.

Lynn

[johnsold]

I was able to get it to filter without generating an error by increasng the number of taps to 433! This results in a filter with a very long transient response. The signal used to generate the image below was 3000 samples of random numbers between 0 and 1.

Lynn