Magnetic and Common Mode Noise

Posted on Monday, May 18, 2015 by Kimberly Versaw

In last week’s blog we talked about static noise and how signal interference can affect cables.  In today’s blog we will take a look at magnetic noise and common mode noise. 

Magnetic fields, radiated by power wiring found in large AC motors, transformers and knife switches, can set up current flows in opposition to the instrument circuit field.  The result is the superimposing of a noise current on the signal current.  The simplest and best means of mitigating the effects of such magnetic interference is by simple twisting of the cable elements.

Common mode interference is the result of currents flowing between different potential grounds located at various points within a system.  Receivers with very high common mode rejection ratios minimize this type of interference.

The next type of noise is crosstalk.  We will discuss this type of noise and noise levels in next week’s blog.


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