Filters Key Terms

Learn some of the key terms for filters

By Emmet McMahan

A filter may refer to a device that uses mechanical or physical means to separate solids from gases or liquids. It typically uses one or more physical barriers that allow the gas or liquid to pass freely, but blocks all or part of the solid material. The degree of separation between the liquids and solids depends on a variety of factors, such as the pore size and thickness of the medium. This type of filtration is widely used in the home to purify drinking water and air, and is also essential in chemical engineering. There also are many other types of filters, such as optical filters which separate one type of light from another.

Bubblepoint test

A bubblepoint test pushes a stream of gas bubbles through a liquid filter under specific conditions. The primary purpose of this test is to measure the size of the largest pores in a filter.
Try: GE Osmonics manufactures a variety of water filters and also provides a glossary of terms for water filtration, including bubblepoint test.

Back pressure

Back pressure refers to a pressure that moves gas or fluid from downstream to upstream from the filter. The occurrence of back pressure is a common consideration in the design of filters.
Try: Nordic Pure makes filters for air conditioners and furnaces. It also provides definitions for a variety of terms that describe filters, such as back pressure.

Angle of incidence

The angle of incidence refers to the angle at which light strikes an optical filter. This angle frequently has a direct affect on the performance of an optical filter.
Try: Optometrics manufactures optical filters and also defines many common terms in optics like angle of incidence.

Capacity

A filter's capacity refers to the amount of solid material that can be removed from the liquid or gas medium. The capacity is measured in different ways, depending on the specific type of filter.
Try: WaterFilters.net provides many resources that relate to water filters, including a definition of capacity.

Absolute filter rating

The absolute filter rating is the minimum particle size at which the filter blocks 99.9 percent of the incoming particles. A filter's absolute filter rating is typically measured in microns.
Try: Aqua Pure Water Conditioning manufactures water softeners and filters, and also offers a glossary of water filtering terms, including absolute filter rating.

Adsorption

Adsorption is a process by which solid particles separate from the molecules of a liquid. Water filters perform adsorption using a variety of physical and mechanical means.
Try: HistoryofWaterFilters.com provides a variety of informational resources on water filters, including a definition of adsorption.