Applications of Standard EMI Filters From Captor Corporation

The rising prevalence of electronic devices across all industries reflects our technologically driven society as well as our increased need for electromagnetic interference (EMI) filters. Without the proper protection against EMI, critical electronic equipment can fail and result in disastrous consequences. It’s more important than ever to invest in reliable EMI filters that serve a broad range of applications.
Here we’ll discuss what EMI filters are, what causes EMI, and the common applications of this essential equipment.

What Are EMI Filters?


An EMI filter is a device typically installed around power supplies and reduces unwanted harmonic energy when the electrical current switches. The EN/CE, FCC, and other military and commercial international EMI standards regulate these filters to minimize or eliminate unintended electronic noise that could disrupt the electronic’s operation. Military applications demand filtration of conducted emissions between 10 kHz to 18 GHz, and commercial applications typically require EMI filtration between 150 kHz and 30 MHz.

EMI filters can be either passive or active and usually cover a specific range of frequencies. Most EMI filters use passive components, such as inductors and capacitors, because they can filter a broader frequency range.

What Causes EMI?

EMI is caused by conducted interference or radiated interference. Physical contact between conductors creates conducted EMI, while non-physical contact, also known as induction, creates radiated EMI. Higher frequencies are associated with radiated EMI, while lower frequencies are associated with conducted EMI.

Where and How Are Standard EMI Filters Used?

Most EMI is high-frequency noise, meaning that the signal’s sine waves are close together. EMI filters contain capacitors and inductors that suppress this noise. Capacitors limit direct current (DC), which carries most of the EMI into a device, and allows alternating current (AC) to pass through. Also called shunting capacitors, capacitors in EMI filters redirect DC within a specific high-frequency range away from a component or circuit. Shunting capacitors then feed this current into the system ground.

Inductors hold magnetic energy as electric currents pass through them, reducing overall voltage. An optimal inductor eliminates the interference completely.

EMI can come from many sources, including power lines, solar flares, power cords, appliances, and more. Thus, standard EMI filters are commonly used in:

  • Radio equipment
  • Lab equipment
  • Medical devices
  • Computers
  • Military equipment

How Does a Standard EMI Filter Work?

EMI in the form of radiated or conducted emissions can be minimized or eliminated by standard EMI filters. The filter’s capacitor creates a low-impedance path to redirect high-frequency signals away from the input. The noise is diverted either back to the power supply or to the ground connection.

Standard EMI Filters From Captor Corporation

EMI filters are essential in reducing electromagnetic interference in electronic devices. They block high-frequency electrical signals so that the device can function without interruption or malfunction.

At Captor Corporation, we offer a variety of custom and standard EMI filters that can help meet the needs of customers in diverse industries. Request a quote today or contact us at 937-667-8484 to learn more about our products and capabilities.

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