Signal-to-noise ratio

Download

• Signal-to-Noise.vi - LabVIEW Virtual Instrument (requires LabVIEW version 2010 or higher)

• Signal-to-Noise.exe - Stand-alone executable (download folder and run setup.exe to install)

• JavaScript version - runs directly in web browser

Description

Signal-to-noise ratio can be defined as the mean value of a signal (S) divided by the standard deviation of the background (N).  The signal becomes impossible to see when S/N drops below 2 or 3.

In this demonstration, a 500-point background of Gaussian white noise is generated with a standard deviation defined by the user.  Then the user-defined signal level is added to four consecutive points in the middle of the array, and the entire array is plotted.  The mean of the four "signal" points is calculated (S), as well as the standard deviation of the background (N).  The actual signal-to-noise ratio (S/N) is calculated and displayed.

(Reference: Skoog, Holler, and Crouch Principles of Instrumental Analysis, 6th Ed Thomson Brooks/Cole 2007)

Front panel

Guiding questions

1. 1. At what S/N value do you see the signal begin to distinguish itself from the noisy background?  (In other words, when would you begin to think there is more than just noise in the data?

   2. At what S/N value would you feel comfortable using the data for a quantitative determination of an unknown concentration?  Why?