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What type of second order filter to choose ?

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Maya

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About filters

Hi, i have a question, i need a second order filter for frequencies of 0.1 Hz but i don't know which one choose if analogic or digital, what do you recommend me, also i need to filter the noise signal of 60Hz.

Thanxx
 

Re: About filters

Usually for these low frequencies a switched capacitor type is used. Linear Technology IC company makes them and has a free design program on their web site.

The problem with switched capacitor filters is that they generate output noise from the switching. If you need low output noise you will have to us an analog active filter or a DSP with 16+ bit ADC input and DAC output.

You can also use the switched capacitor filter followed by an active filter with wider bandwidth to remove most of the output noise. The reason for wider bandwidth is economic. The size and cost of capacitors for your 0.1 Hz bandwidth would be huge.
 

Re: About filters

I would use digital filtering through programming, such as assembly/C coding on a microcontroller, or a PC if you use it to process data. In any case, you need an analog filter in the data acquisition channel to cut out the high frequencies. It can be at 40 Hz.
 

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