EMI, or Electromagnetic Interference, causes unwanted interference and degradation in electronic devices, wiring, control loops, and instrumentation systems. Preventative measures and reduction techniques, such as grounding and decoupling, can help reduce or eliminate EMI.
This simple walkthrough will teach you how to reduce the effects of EMI by identifying four of the most common preventative measures and elimination methods.
Shielding
Shielding blocks electromagnetic fields through the use of conductive or magnetic barriers. It can reduce or eliminate the coupling of radio waves, electromagnetic fields, and electrostatic fields.
The effectiveness of this method relies on the shielding’s overall construction—material, thickness, and size—and the intensity of the electromagnetic noise.
Shielding can be made from sheet metal, like copper and steel, metal screen, and metal foam.
Solid and braided shields are two commonly used types. The best noise reduction is achieved through solid shields. As an unfortunate downside, this type is difficult to manufacture and apply, making it expensive and hard to obtain.
Braided shields are less effective, covering only 60 to 95 percent of the wiring, but offer increased flexibility and strength.
Vacuum metalizing is another innovative, cost-effective type of shielding application.
Twisted Pair Wires
Using twisted pair wires or coaxial cables is the easiest method for reducing and preventing EMI. Crossing or twisting the wires forces them to occupy a compact space, which reduces the loop area, and, in turn, induced voltage.
This method’s effectiveness is dependent on the number of twists per unit length.
Grounding
Grounding is another effective—and inexpensive—method for controlling EMI. Grounds close the current loop and act as a type of return path for currents.
For low-frequency applications, single-point grounds are ideal. The function of single-point grounds is exactly what the name suggests. It references or connects everything to a single, solid point.
When equipment is bonded to the same point, less current will flow between them. This reduces the ability of interference currents to tamper with signal currents, therefore reducing the effects of EMI.
When there’s more than one conductive loop between equipment, a ground loop exists. This is a massive cause of interference. Issues that stem from ground loops can be eliminated through the creation of a low or zero-impedance ground or by providing separate ground paths for currents.
Decoupling
Without the existence of two interconnected coupling channels, electromagnetic interference is impossible. Decoupling or severing these channels can minimize or, in certain cases, fully eliminate the effects of EMI.
Decoupling capacitors are used to decouple sections of an electrical network. They suppress the effects of high-frequency noise and reduce their effect on the overall circuit.
