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Gain Vs. Frequency meter - Where would I start?

 

Hey guys,

I've been reading the latest posts about various scopes and the pro's
and con's of each and that got me thinking about a (hopefully) small
project of a gain vs. frequency meter. The device would take an
input signal and display the relative db of each frequency present in
the signal. Similar to the Forier Analysis in PSpice. The reference
voltage should be variable and it doesn't have to have an exremely
wide bandwidth - audio range would be enough. A graphic LCD could
then be used to display the output.

My question is, what would be needed for a device like this. I know
that an input buffer/isolation stage (unity-gain OP-AMP's) to provide
a high-impedance input will be needed, and the magnitude comparison
can be achieved with either a compariator or an op-amp. I can
program a PIC to display the output, but what would be needed in the
middle? How would I seperate out each frequency? Also, would this
device be considered a "Frequency Counter"?

Thanks for any tips,

Shawn
Stefan Trethan
 

On Sun, 08 Oct 2006 08:27:57 +0200, sstandfast <sstandfast@...> wrote:

Also, would this
device be considered a "Frequency Counter"?
Thanks for any tips,
Shawn

No, it would be considered a spectrum analyzer.

ST
Leon Heller
 

----- Original Message -----
From: "sstandfast" <sstandfast@...>
To: <Electronics_101@...>
Sent: Sunday, October 08, 2006 7:27 AM
Subject: [Electronics_101] Gain Vs. Frequency meter - Where would I start?


Hey guys,

I've been reading the latest posts about various scopes and the pro's
and con's of each and that got me thinking about a (hopefully) small
project of a gain vs. frequency meter. The device would take an
input signal and display the relative db of each frequency present in
the signal. Similar to the Forier Analysis in PSpice. The reference
voltage should be variable and it doesn't have to have an exremely
wide bandwidth - audio range would be enough. A graphic LCD could
then be used to display the output.

My question is, what would be needed for a device like this. I know
that an input buffer/isolation stage (unity-gain OP-AMP's) to provide
a high-impedance input will be needed, and the magnitude comparison
can be achieved with either a compariator or an op-amp. I can
program a PIC to display the output, but what would be needed in the
middle? How would I seperate out each frequency? Also, would this
device be considered a "Frequency Counter"?
More like a spectrum analyser. Lots of audio spectrum analyser programs are available that use the PC sound card, they just do an FFT on the input signal. An application for a dsPIC evaluation board does an FFT and displays the spectrum on an LCD, an ordinary PIC won't have enough processing power.

Leon
LT Ron Wright
 

Shawn,

Sounds as if you will need a tunable filter so you can select the
various frequency components.

73, ron, n9ee/r




--- In Electronics_101@..., "sstandfast"
<sstandfast@...> wrote:

Hey guys,

I've been reading the latest posts about various scopes and the
pro's
and con's of each and that got me thinking about a (hopefully)
small
project of a gain vs. frequency meter. The device would take an
input signal and display the relative db of each frequency present
in
the signal. Similar to the Forier Analysis in PSpice. The
reference
voltage should be variable and it doesn't have to have an exremely
wide bandwidth - audio range would be enough. A graphic LCD could
then be used to display the output.

My question is, what would be needed for a device like this. I
know
that an input buffer/isolation stage (unity-gain OP-AMP's) to
provide
a high-impedance input will be needed, and the magnitude
comparison
can be achieved with either a compariator or an op-amp. I can
program a PIC to display the output, but what would be needed in
the
middle? How would I seperate out each frequency? Also, would
this
device be considered a "Frequency Counter"?

Thanks for any tips,

Shawn

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