FIU CHM 4130 - CHAPTER 5_Xiao_Signal_To_Noise_2018 (58 pages)

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CHAPTER 5_Xiao_Signal_To_Noise_2018



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Chapter 5 Signals and Noise Signal to Noise Ratio Types of Noise Signal to Noise Ratio Enhancement Signal Averaging Filtering Signal and Noise The signal is what you are measuring that is the result of the presence of your analyte Noise is extraneous information that can interfere with or alter the signal It can not be completely eliminated but hopefully reduced Noise is considered random indeterminate SIGNAL with NOISE SIGNAL with NOISE averaged out The reason for a Signal to Noise Ratio The average strength of the noise N is constant and independent of the magnitude of the signal Signal vs Noise Why is a Signal to Noise Ratio Signal to noise ratio S N Parameter describing quality of data often referred to as figure of merit What is a Signal to Noise Ratio Signal mean X Noise standard deviation s This is mathematically the inverse of the RSD or we can say that S 1 N RSD S N 4 3 1 Very little confidence in ability to determine peaks S N 43 1 Signal and Noise 1 What are signal and noise 2 Why is using a signal to noise ratio 3 The relationship between signal to noise ratio and RSD S N Objective A S N ra o of 3 is usually the minimum that is acceptable Increase the signal to noise ra o More signal vs noise means a lower STDEV More precise measurement Lower STDEV means a be er LOD Lower limits of detec on Reduce as much of the noise as possible by carefully controlling condi ons Temperature power supply varia ons etc etc etc Noise Types of Noise in Chemical Analysis 1 Chemical Noise 2 instrumental noise Types of Noise 1 Chemical Noise Undesired chemical reac ons in the System being analyzed Examples Temperature Position of chemical equilibria Pressure Humidity Moisture content of sample Vibra ons Stratification of powdered solids Light intensity Photosensitive materials Fluctua ons uncontrolled variables Types of Noise 2 Instrumental Noise Noise from instrumental components a complex composite several types sources A ects all types of instruments Can oSen be controlled



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