Chapter 5, Problem 5.1QAP

Interpretation Introduction

Interpretation:The type of noises which are frequency dependent or frequency independent needs to be determined.

Concept introduction:Chemical analyses are related with two types of noise which are chemical noise and instrumental noise. Chemical noise is due to reasons that affect the chemistry of the system being analyzed. Instrumental noise is components of the instrument. There are four types of instrumental noises, they are thermal noise, shot noise, flicker noise and environmental noise.

Answer to Problem 5.1QAP

Flicker noise and environmental noise are frequency dependent.

Thermal noise and shot noise are frequency independent.

Explanation of Solution

Thermal noise can be calculated according to below equation:

${\overline{V}}_{rms}=\sqrt{4KTBR}\times 10$

Here,

${\overline{V}}_{rms}$ = Thermal noise

K = Boltzmann’s constant

T = Temperature

B = Band width

R= Resistance

According to above equation, thermal noise is dependent on band width but independent of frequency itself. Like thermal noise, shot noise is thus the same at any frequency.

Flicker noise is inversely proportional to the frequency being observed. It is frequency dependent.Environmental noise is a combination of different forms of noises that arise from the surroundings. Therefore, environmental noise is frequency dependent.

Conclusion

Here, it can be concluded that flicker noise and environmental noise are frequency dependent, while, thermal noise and shot noise are frequency independent according to above explanation.