# Shutting out mains voltage frequency 50/60Hz

A

#### Ant_Magma

Jan 1, 1970
0
In this application note by ST

www.st.com/stonline/books/pdf/docs/1752.pdf

On page 6, section III- Measure on mains, it used the equation:

Fc=(Rtotal*C*2*pi)=1.1kHz

But when i calculated the values 6250*2.2e-9*2*pi, i got 8.639e-5.
What's wrong?

Another thing, i thought the equation for cutoff frequencies were
Fc=1/(2*pi*R*C)?

W

#### w2aew

Jan 1, 1970
0
The document is wrong, on two counts! The equation for Fc in a simple
RC circuit is 1/2piRC as you've stated (they left out the 1/ part, or a
(-1) exponent). Also, they calculated wrong - it should be 11.6KHz,
not 1.1KHz.

P

#### Phil Allison

Jan 1, 1970
0
"w2aew"
The document is wrong, on two counts! The equation for Fc in a simple
RC circuit is 1/2piRC as you've stated (they left out the 1/ part, or a
(-1) exponent). Also, they calculated wrong - it should be 11.6KHz,
not 1.1KHz.

** Not to mention the danger and stupidity of connecting the chassis ground
of an Spectrum Analyser to the supply neutral.

I note the article was written by two frogs.

Beware - they are really toads.

......... Phil

A

#### Ant_Magma

Jan 1, 1970
0
D**n!

I wonder how many papers and ANs i have that has such mistakes. Don't
they ever check before they publish?

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