filters while acquiring data

[Mudda]

Hi,

I am using "DAQmx Read" function to read 15 channels data from a PXI 6259 Card at a sampling rate of 2.5k. Out of the 15 channels, if I want to apply a low pass butterworth filter on two channels prior to DAQmx Read is possible to do, I mean during the channel configuration can I do it so that the "DAQmx Read" function reads filtered data from those two channels and raw data on other channels?

Thanks,

Mudda.

[aeastet]

You can do this. I would reccomend that you have two seperate loops. One for data acquisition and one for processing the data. You could index the first two arrays and filter them and use the rest of the data in it's raw form.

[Mudda]

Hi,

Thanks for the reply, I would like to avoid any data processing after I collect the data. I am looking for a solution so that I can assing a property or something similar to the DAQmx task so that I can read the data which is already filtered for me.

Mudda.

[aeastet]

You are going to have to use a hardware filter for that. I do not believe that there is a way for you to filter directly as the channel is being sampled.

[LV_Pro]

I'm not sure what you are asking. Are you asking if it is possible to do a software (LabVIEW) butterworth filter on two channels before DAQmx READ? If so I would answer no, the data isn't present until the DAQmx read. If you are using a hardware filter on the those two channels before the DAQ, then yes, you just need to keep track of which channels are filtered and which are "raw". Basically you will be getting an array of values, two elements (or rows if you are getting multiple samples each time) represent the filtered data. If not a hardware filter then you will have split the two channels off to run them through the filter algorithms.

aeastet, you type faster than I do.

Message Edited by LV_Pro on 01-11-2010 03:27 PM

[Mudda]

Hi,

you answered my question in the first answer. I knew that either I have to do a post process on the data manually or I have to use a hardware filter before the actual DAQ card but I was hoping to avoid any manual filtering on the data by assinging a filter setup or some sort of it to the DAQmx Task. It seems like I don't have that option.

I appreicate your replies.

Mudda.