Signal to Noise Ratio

[WaldoMcFroog]

I have a formula to work out signal to noise ratios:

S/N = 20 log10(Vs/Vn)

Where Vs=the incoming signal strength
and Vn=the noise level
both in microvolts.

Assuming Vs=10, Vn=1, I want to work this out using Excel. However, I'm not sure what the syntax of the equation is telling me!

Am I multiplying 20 by the result of log10(Vs/Vn) or
am I multiplying 20 log10 by the result of (Vs/Vn)?

Any assistance gratefully received!

[CT]

I think it's the first one, as that follows standard notation for a log equation. But, i'd let someone else confirm this. Maybe post in Science too.

[Buenchico]

The '10' in the formula is simply the base of the logarithms. It should be written as a suffix. See here:
http://en.wikipedia.org/wiki/Signal-to-noise_ratio

To use the formula, divide Vs by Vn. Take the log of the result. (The '10' just tells you to use the 'log' key on your calculator -which gives logs to the base 10 - rather than the 'ln' key which gives logarithms to the base e). Now multiply by 20.

(I don't use Excel but I hope that you can work out the way to do it from this information. Meanwhile, I'll take a look at Excel and post again if I come up with anything useful).

Chris

[kempie]

The Excel formula would be exactly as you wrote in the question... =20*LOG10(A1/B1)

[WaldoMcFroog]

That's really helpful! Many thanks for your responses!