Electromagnetic noise (interference) is always present in a measurement system. The desire to minimize noise in your signal of interest can only be accomplished after the noise is properly identified. This paper summarizes a mechanical engineering undergraduate laboratory activity developed for ME 370 – Engineering Measurements and Instrumentation at Iowa State University. The goals of this activity are to (i) develop an understanding of how analog noise enters a measurement system and (ii) investigate several noise reduction methods. Students induce and measure capacitively coupled noise and investigate how the noise is related to noise source frequency and measurement circuit resistance. Methods to minimize capacitively coupled noise, including electrical shielding, are introduced and tested. Inductively coupled noise is then demonstrated, and the use of twisted pair wiring is shown to reduce this type of noise. Finally, conductively coupled noise is demonstrated through ground loops. Once this laboratory exercise is completed, students have an appreciation for how electromagnetic noise may be introduced into a measurement system, and how the effects of this noise can be minimized.
Available at: http://works.bepress.com/sriram_sundararajan/8/