June 18, 2006
June 18, 2006
June 21, 2006
11.392.1 - 11.392.13
Demonstrating Electromagnetic Noise in an Undergraduate Measurement and Instrumentation Course
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.
Mechanical Engineering Measurements and Instrumentation, commonly referred to as ME 370 at Iowa State University (identified as ME 370 in this paper), is a required course in the mechanical engineering undergraduate curriculum. The course covers various measurement and instrumentation topics, as well as data acquisition and analysis. Since electromagnetic noise is part of every measurement system[1-4], it is important for students to be able to recognize its source. The goal of this paper is to describe laboratory activities that were initiated in ME 370 to demonstrate how electromagnetic noise is introduced in a measurement system, and how the effects of noise can be minimized.
The most common type of measurement noise is intrinsic noise, which is random noise that is always found in any physical circuit. The noise is manifested as a result of the laws of particle (electron) behavior on a microscopic scale. Thermal noise (also called Johnson or white noise) is an example of intrinsic noise; it is due to random vibrations of electrons in a conductor and will be present at any temperature above 0K. This type of noise is not the focus of this ME 370 laboratory activity or this paper.
Interference noise is caused by an unwanted stray signal that is electromagnetically coupled to a measurement circuit from a nearby source via various means. This type of noise directly affects measurement systems. The most common type of interference noise is line noise (e.g., 60 Hz in North America). Line noise can enter into a measurement system in a variety of ways including close proximity to power cords or industrial equipment, poor grounding techniques, and/or the use of poorly designed measurement systems. In general, interference
Muff, D., & Heindel, T., & Sundararajan, S. (2006, June), Demonstrating Electromagnetic Noise In An Undergraduate Measurement And Instrumentation Course Paper presented at 2006 Annual Conference & Exposition, Chicago, Illinois. https://peer.asee.org/493
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