static noise

Two Minute Penalty for Signal Interference

Posted on Wednesday, May 13, 2015 by Kimberly Versaw

Signal interference is when unwanted signals are trying to get in the way of a useful signal.  The absence of interference is critical when working with cable applications.  When a particular installation is prone to EMI/RFI/ESI interference from either internal or external sources, some form of cable shielding will be required.  The types of interference—or noise—cables are exposed to can determine the type of cable shielding required.  There are basically four types of noise which will affect the wiring or cabling of an instrument or control circuit: static, magnetic, common mode, and crosstalk noise.

This blog series will go over the different types of noise and how to properly shield your cable in order to inhibit signal interference.  We’ll start off with static noise.

Static noise refers to signal distortion due to the electrical field radiated by a voltage source, which has coupled into the signal-bearing circuit.  Simple shielding of the full circuit is a typical means of mitigating this electrostatic type of interference.  Foil shields, which offer 100% shielding efficiency, have proven most effective against this type of interference.  It is critical that the shield be continued to, and completely encompass, the transmitting and receiving ends of the circuit if high levels of noise reduction are required.  Furthermore, effective grounding of the shield is also required; “floating” or non-grounded shields only partially reduce the effects of noise.

Now that we have the basics of signal interference and shielding, our next blog will explore magnetic and common mode noise.


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