analog vs digital filtering

[mbhatti2000]

Dear All,

I would like to ask, why are companies still using analog filters. All the filtering can easily be done by digital filtering. Why is the need of analog filters still necessary. All the filtering can be done by digital filters in LabVIEW.

I want to eliminate 50Hz noise from EEG. Cant I just record the signal and eliminate 50Hz noise. Is a filter implemented in hardware better?

why should I use analog filters when I can use digital filters. And any way I have more options when using digital filtering and I do not loose the neighboring frequencies, in a band stop filter when I use digital filters.

thank you.

Munir Afzal Bhatti 

[ceties]

For example when you are making real-time measurement with a lot of dataprocessing the analog way is significantly faster and doesn't require the power of the computer.

I think there are people that will give you many other right answers

[gwd]

A completely passive analog filter can sometimes remove strong interfering signals before the A/D, making it possible to use a cheaper, lower resolution A/D for the same performance. This is what the AC coupling selection does. In principle you could just digitize the AC+DC to very high resolution, and then filter later. Same thing for prefilters or preselectors in RF systems. Another example is the bandwidth limit on high speed oscilloscopes;  no point in digitizing all the noise up to 100 MHz if there's nothing interesting up there.

In general when alternate engineering solutions survive it's because neither one solves all problems.