Types of Filters

Filters are systems or elements used to remove substances such as dust or dirt, or electronic signals, etc., as they pass through filtering media or devices. Filters are available for filtering air or gases, fluids, as well as electrical and optical phenomena. Air filters are used for cleaning the air. Electronic filters clean electrical signals of unwanted frequencies in the audio and intermediate ranges while RF and microwave filters have the same function but in the radio and microwave frequency range. EMI and RFI filters minimize or eliminate electromagnetic interferences. Fluid filters remove debris from fluids. Fuel filters remove contaminants from fuels, while hydraulic filters remove contaminants from hydraulic fluids. Water filters clean water, not only for drinking and swimming but in water treatment plants as well. Optical filters pass light and filter light wavelengths.

Air Filters
Air Filters are systems or components that remove particulates from air as it passes through filtering elements and can be complete systems or replacement elements alone. Key specifications include the intended application, physical size, filter type, filter media, and air flow rate. Air filters are used in systems that require particulate-free air. They are used also to clean the air before exhausting it. An air filter system usually consists of a filter element and the housing that contains the element. They come in shapes for specific applications such as automobile engines, cleanrooms, range hoods, or furnaces. An air filter can remove a variety of filtrands including dusts, fumes, oils, and bacteria.

Electronic Filters
Electronic Filters are used primarily to process electronic signals by removing unwanted frequency components or enhancing others. They usually operate at frequencies below RF (radio frequency). Typical operating frequencies ranges are AF (audio frequency) or IF (intermediate frequency), both of which are power frequencies. There are many types of, and functions for, electronic filters including passive or active, analog or digital, and low pass and high pass. Electronic filters are also used to minimize or eliminate electrical noise.

EMI/RFI Filters
EMI/RFI Filters are electrical devices that eliminate or minimize EMI (electromagnetic interference) or RFI (radio frequency interference) within a system. Key specifications include the intended application, filter type, electrical characteristics including voltage, current, and frequency ratings, as well as bandwidth. EMI/RFI filters are used primarily in electronic and telecommunication applications to minimize or eliminate EMI or RFI signals that interfere with the performance of an electrical product or system. The filter is normally placed between an AC power line and the equipment requiring protection. Versions can also be placed on PCBs, incorporated in connectors, or used as stand-alone components for mounting in utility cabinets. The filters may also work to eliminate EMI/RFI emissions from the equipment.

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