Low frequency signal

PoisoN_83

Hello!

I´m new here and need a little help with some electronics.

I have signals with information in the 0.2Hz - 5 Hz range (breath signal) with a DC offset of about 3V (not constant).
I want to eliminate this offset voltage but still don´t change the original information.
What type of highpass filters can I use for this application?
How should I think?
Information about both analog and digital filter of this type is interesting.

Thank you!

waht

You just need to run the signal through a capacitor. DC voltage will be blocked and AC will run right through. For low frequencies you need more capacitance to minimize its impedance. A 1000 uF cap would do.

berkeman

Or if you want to use a smaller capacitor, just make an opamp-based highpass filter.

And if you can just digitize the signal, then you can write a simple digital HPF routine as you suggest to get rid of the slowly-varying DC offset.

http://en.wikipedia.org/wiki/Electronic_filter

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waht	You just need to run the signal through a capacitor. DC voltage will be blocked and AC will run right through. For low frequencies you need more capacitance to minimize its impedance. A 1000 uF cap would do.

berkeman Mentor	Or if you want to use a smaller capacitor, just make an opamp-based highpass filter. And if you can just digitize the signal, then you can write a simple digital HPF routine as you suggest to get rid of the slowly-varying DC offset. http://en.wikipedia.org/wiki/Electronic_filter