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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.

Captor Corporation Announces Release of MIL-COTS EMI Filter Line


Tipp City, OH. May 2020 – Captor Corporation is excited to announce the release of our MIL-COTS EMI Filter series. The new series is available in AC Single Phase (250VAC), Three Phase Delta (120/208VAC), Three Phase Delta (254/440VAC), Three Phase Wye (254/440VAC). The different voltage levels can be supplied for 50/60 Hz or 400 Hz applications. The filters feature low capacitance to ground to meet MIL-STD-461 Navy applications.

Captor also offers the option of modifying the filters to meet your specific mechanical and power requirements. Our experienced Engineering and Manufacturing team will design the modified COTS at no extra cost to the customer and offer competitive delivery times.

“We are extremely pleased with the initial interest from our customers concerning this product line. Not only are we selling them right out of the catalog, but we have already tailored many filters to fit the exact application,” says Scott Timms, President.

Captor Corporation Announces Rafik Stepanian as Chief Engineer

Tipp City, OH. April 2019 – Captor Corporation, a leading manufacturer of EMI Filters, HEMP Filters, Tempest Filters, Cable Assemblies and Contract Manufacturing is pleased to announce Rafik Stepanian as Chief Engineer.  Rafik supports the Tipp City manufacturing facility and will also maintain an office and lab in Philadelphia.

With over 25 years of experience in the EMC/EMI industry Rafik possesses an exceptional knowledge of filter design and EMI compliance testing.  He has worked with all the Prime Defense Contractors offering solutions for stringent EMI compliance standards. Commercial aviation, industrial and medical customers have also routinely seek out Rafik’s expertise for their challenging projects.

Rafik’s diverse experience includes client account management, project, contract and product management as well as manufacturing process optimization.  He is also available for on-site EMI consulting/training for customer engineering teams.

“Captor is excited to welcome Rafik to our team. With his vast experience and knowledge, we have expanded our ability to bring new solutions to the marketplace. This will benefit not only Captor, but all of our customers and future clients,” says Scott Timms, President.