# The Naked Scientists Forum

### Author Topic: How do I filter electrical noise?  (Read 4592 times)

#### Atomic-S

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##### How do I filter electrical noise?
« on: 15/10/2006 02:42:31 »
Supposing that I have an electrical signal that occupies the band 0 to 80 KHz, and I want to filter out (reduce to less than 1% of their former amplitudes)all the portions that fall below 32752 Hz, while keeping (losing or gaining no more than 25% amplitude) all portions above 32784 Hz.  And I have a reference signal available at 32768 Hz. What is the best way to accomplish this?
« Last Edit: 24/12/2006 09:18:56 by chris »

#### Soul Surfer

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##### Re: How do I filter electrical noise?
« Reply #1 on: 15/10/2006 21:52:38 »
Looks like a good use for a digital filter but at first glance your requirements look quite demanding.  I can't tell you the answer off the cuff but look up digital filter theory.

Assuming your signals are analogue ones you will have to sample your signal at a rate a few times your highest frequency and probably chose your sampling rate to be related to your reference frequency.  the accuracy of sampling will depend on the dynamic range you require  (so far this has not been specified).  Achieving your required filter characteristics is then a matter of applying the required digital processing algorithms using processors fast enough to perform the calculations at your chosen sampling rate.  With modern computers or DSP chips this should present nop insurmountable problems at this datarate

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#### another_someone

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##### Re: How do I filter electrical noise?
« Reply #2 on: 15/10/2006 22:10:36 »
Would it be something that one could use a ceramic filter for?

George

#### Soul Surfer

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##### Re: How do I filter electrical noise?
« Reply #3 on: 18/10/2006 11:16:31 »
Not unless it is for a standard application.  Ceramic and crystal filters need to be mass produced for specific frequencies and bandwidths because their structure defines the frrequency that the filter operates.

Analogue and digital filters can be dedigned and tuned by anyone and do not require the precise grinding and polishing of lumps of material

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#### The Naked Scientists Forum

##### Re: How do I filter electrical noise?
« Reply #3 on: 18/10/2006 11:16:31 »