"Hank2" wrote in message . com...
Thank you Dick Pierce for your thoughtful reply to my question. Being a
"digital" power meter, I have assumed that the "averaging" process is
carried out digitally since we are talking of integration times up to 200
seconds.

Not necessarily...

Presumably, the meter takes the pressure from its microphone, converts that
linearly to voltage, then performs the operations of squaring the voltage to
get the power, then compressing this power logarithmically to arrive at dBs.
Just where in this sequence, the "average" is taken is the point on which I
am not clear.

Not necessarily. It's also possible that the averaging is, in fact,
done with a simple analog leaky integrator with a long enough time
constant, and the "digital" portion is nothing more than an
inexpensive digital display of the result. They can even get the dB
scaling by taking the averaged linear voltage, digitizing it then
run it through a ROM lookup table to convert linear volts to dB. Very
simple to design, very inexpensive to implement.

More careful experiments, where I took "averages" over times up to 120
seconds while turning the noise source on and off with a 50% duty cycle,
yielded an "average" reading that was approximately 6 dB below the noise
source power. This would suggest to me that the averaging is being done on
the microphone output voltage (half voltage equals -6db power drop).

Yup, sounds about right.

However, It would be great if someone has actual knowledge of the power
meter circuitry and its functions. Any offers?

Alas, I have no specific knowledge of this unit.