How to caculate SNR using SINAD and THD?

[amandarila]

Hello Everyone,

I want to caculate Signal noise ratio(donot include distortion),but I just use Distortion Measurements to get SINAD(dB) and THD, I donot know how to get the real value of SNR, I have searched all the topic about SNR in

board, nobody give a formula to compute it.

So, anybody can give me a hand?

[amandarila]

I google from internet that:

             P(signal)+P(noise)+P(distortion)

SINAD= ------------------------------------------------ 

              P(noise)+P(distortion)

 and 

              P(all the harmonic power)+P(noise)

THD=    ----------------------------------------------------------

                    fundamental power

so, do SNR have any relationship with SINAD and THD?

[EvenDeejay]

Signal to noice ratio

It says that SNR = Psignal/Pnoise

If you know Pdistortion you can use the SINAD formula and make it into the SNR formula. Otherwise you should look away from the SINAD and THD. To find SNR you have to know Psignal and Pnoise.

THD also depends on the harmonics. I would say that SINAD and THD are built on the SNR formula so there is a relationship between them. You can use the other fiormulas to find an exspression for the Psignal or Pnoise if you don't know the values for them, but know for example the distortion.

[perumpral]

hello, did you computed the thd value in dB? Does the distortion measurement pallet for finding out the thd gives the Db value?

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