Signal to noise

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lakshminarayana
lakshminarayana's picture
Signal to noise

sir can u explain meaning  of drift and  noise, other one is purpus of signal to noise ration in hplc

Dr. Analytical
Dr. Analytical's picture
Noise is the random

Noise is the random variations in the instrrument signal.  Every instrument has some noise that is caused by the components in the instrument. 

Drift is a regular change in the signal, usually toward a higher or lower signal value.  The amount of change is more than the noise.

The signal-to-noise ratio (S/N) tells us how big a signal is compared to the noise.  When this ratio is larger than some value (usually 3), we have some confidence that what we are observing is a real change above the normal noise, and not just normal variations.  This concentration or mass that produces this ratio represents the Limit of Detection (LOD) for the instrument.  This is the smallest amount that we can detect.  Any peaks that are smaller than this value may actually be noise and not real peaks.  

It is important to know this amount.  You can not report the presence of a peak is the ratio is smaller than the LOD.