Low Frequency Signal Processing - Filtering DC Offset

In summary, the individual is seeking assistance with electronics and specifically wants to eliminate a DC offset while preserving the original information in signals ranging from 0.2Hz to 5 Hz. They are looking for suggestions on highpass filters, both analog and digital, and are considering using a capacitor or an opamp-based filter. They are also interested in resources for learning more about electronic filters.
  • #1
PoisoN_83
1
0
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!
 
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  • #2
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.
 
  • #3
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
 

What is a low frequency signal?

A low frequency signal is a signal that varies slowly over time, typically between 0 and 200 Hz. This type of signal is commonly found in audio and biomedical applications.

What is DC offset?

DC offset is a constant voltage or current present in a signal that is not changing over time. It can occur when a signal is measured or transmitted, and can affect the accuracy of the signal.

Why is filtering DC offset important in signal processing?

Filtering DC offset is important because it removes any unwanted constant voltage or current from a signal, allowing for a more accurate representation of the desired signal. This is especially important in applications where precise measurements are required.

What are the common methods used for filtering DC offset?

The common methods used for filtering DC offset include high-pass filters, notch filters, and subtraction techniques. These methods can be implemented using analog or digital filters, depending on the application.

Can DC offset be completely eliminated from a signal?

No, it is not possible to completely eliminate DC offset from a signal. However, it can be reduced to a negligible level through careful design and implementation of filtering techniques.

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