>On Tue, 10 May 2005 12:22:45 GMT, Oliver.Zind@web.de (OZ) wrote:
>
>>Hi,
>>I am searching a mathematical solution for a notch filter.
>>
>>I measured a signal with a ADC and I want to kill one frequency (50Hz)
>>out of the measurement data.
>>
>>Does anyone of you know a mathematical function for a notch filter ?
>>
>>best regards
>>Oliver
>
>Hi,
>
> here's an efficient 3-tap FIR filter that you might
>want to consider. The filter's 1st and 3rd coefficients
>are both ones. The center coefficient is
>
> -2cos(2*pi*Fn/Fs)
>
>where Fn is the notch location in Hz, and Fs
>is the sample rate in Hz.
>
>Good Luck,
>[-Rick-]
>

Reply by Rick Lyons●May 16, 20052005-05-16

On Tue, 10 May 2005 12:22:45 GMT, Oliver.Zind@web.de (OZ) wrote:

>Hi,
>I am searching a mathematical solution for a notch filter.
>
>I measured a signal with a ADC and I want to kill one frequency (50Hz)
>out of the measurement data.
>
>Does anyone of you know a mathematical function for a notch filter ?
>
>best regards
>Oliver

Hi,
here's an efficient 3-tap FIR filter that you might
want to consider. The filter's 1st and 3rd coefficients
are both ones. The center coefficient is
-2cos(2*pi*Fn/Fs)
where Fn is the notch location in Hz, and Fs
is the sample rate in Hz.
Good Luck,
[-Rick-]

Reply by Rimmer●May 15, 20052005-05-15

"OZ" <Oliver.Zind@web.de> wrote in message
news:4280a789.21786457@news.btx.dtag.de...

> Hi,
> I am searching a mathematical solution for a notch filter.
>
> I measured a signal with a ADC and I want to kill one frequency (50Hz)
> out of the measurement data.
>
> Does anyone of you know a mathematical function for a notch filter ?
>
> best regards
> Oliver

A high-pass filter should do the trick - don't need a notch normally.
Rimmer

Reply by OZ●May 13, 20052005-05-13

Hi,
thanks a lot for the tips. I will check.
Greetings Oliver

Reply by robert bristow-johnson●May 10, 20052005-05-10

in article yg2ge.198756$cg1.137609@bgtnsc04-news.ops.worldnet.att.net,
Charles Krug at cdkrug@worldnet.att.net wrote on 05/10/2005 09:01:

> On Tue, 10 May 2005 12:22:45 GMT, OZ <Oliver.Zind@web.de> wrote:

...

>> I measured a signal with a ADC and I want to kill one frequency (50Hz)
>> out of the measurement data.
>>
>> Does anyone of you know a mathematical function for a notch filter ?
>
> There are infinitely many, though I suppose you can limit yourselves to
> analog filters that are practical to construct and digital filters that
> fit in your time/memory constraints.

if the latter (digital filter), you can check out the biquad notch filter at
the Audio EQ Cookbook at harmony-central.com .
--
r b-j rbj@audioimagination.com
"Imagination is more important than knowledge."

Reply by Mark●May 10, 20052005-05-10

Be aware that if you have a signal contaminated by AC line noise, that
this line noise often contain harmonics of the 50 Hz (or 60Hz in the
US) as well.
If it sounds like a BUZZ instead of a hum, it has harmonics.
Mark

Reply by Charles Krug●May 10, 20052005-05-10

On Tue, 10 May 2005 12:22:45 GMT, OZ <Oliver.Zind@web.de> wrote:

> Hi,
> I am searching a mathematical solution for a notch filter.
>
> I measured a signal with a ADC and I want to kill one frequency (50Hz)
> out of the measurement data.
>
> Does anyone of you know a mathematical function for a notch filter ?
>

There are infinitely many, though I suppose you can limit yourselves to
analog filters that are practical to construct and digital filters that
fit in your time/memory constraints.
Take a look at the Scientist and Engineer's Guild to DSP over here:
http://www.dspguide.com/pdfbook.htm
Read chapters 14-21. There are examples of exactly what you want to do.
Charles

Reply by OZ●May 10, 20052005-05-10

Hi,
I am searching a mathematical solution for a notch filter.
I measured a signal with a ADC and I want to kill one frequency (50Hz)
out of the measurement data.
Does anyone of you know a mathematical function for a notch filter ?
best regards
Oliver