Thanks Alain for the ideas. I suppose one has to do it in practice and check the response of the circuit.

The PIC is not yet defined. I will choose one after we will end with the spec's (memory needed etc).

Quote Originally Posted by mister_e View Post
mmm, kinda mix with embedded strings in your code space and lookup table...
So the Excel sheet would have to pack it in 14Bit and later you use DA.

How's that sound? pretty bad to me as the unpacking method will certainely be slightly longer to execute than reading a single Byte for a DT, DW table ...
Steve, I agree that I have to pay for the extraction in terms of speed. But then, I guess, somewhere in the program there will be a point needing mcu power as it seems.

Now, Darrel, as Nikos (Savnik) stated, 3db is indeed a double or half the power. But as for voltage, you need 6db.

db(Watts)=10*LOG*(P1/P2)

db(Volts)=20*LOG*(V1/V2)

For the case we discuss, replace the V2 with 0.775Volts or the P2 with 1mW.

If you make the maths you can prove it.

Relative to the dynamic range, well I have to measure from 7.75mV up to 1.55 RMS or from 11mVpk up to 2.19Vpk. Lets make it easier and the MAX be 2Vpk.

I will Scale it to max 5Volt (x2.5), so the minimum will be 11mV*2.5=27.5mV.

For a 10-bit ADC the LSB will be 4.88mV, so a 10-bit ADC will be enough for a 46db dynamic range. If I am wrong please correct me.

Now, about the CA3089 or the better one that I used long ago, CA3189. Where does this chip fit here?

A big thank you to all responded.

Ioannis


P.S. The idea of Select Case may also be a nice alternative since for every BAR in the Bargraph there are alo of values to fit. It will be a long Select case of course... I have to try it.