On Thu, Feb 03, 2000 at 07:44:05PM -0600, Anthony Clay wrote:
> The part I am having to think about is how to accurately measure the final
> dB signal level. Here is the situation:
>
Hmmm.... I remember reading somewhere an article in a trade rag that showed
using some derivative of an AGC circuit to measure signal output.  If I can
find the article in my archives (fat chance) I'll re-read it and post what
I find.

I would be tempted to use the full wave rectifier approach, using a filter
cap to smooth it out, and sampling.   The trick here as I recall is to keep
the value of the cap sufficiently large enough to do the filtering but not
so large as to cause a "rubber screwdriver" effect.

On the other end of the scale is a problem of aliasing. If your sample is
taken at the wrong time you could be reading "off peak" values for amplitude
and therefore not the real amplitude.  Of course this is where your filter
cap comes in.

It's been a while since I have thought about these subjects so I may well be
off here....


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Peter L. Berghold                        Peter@Berghold.Net
"Linux renders ships                     http://www.berghold.net
 NT renders ships useless...."