Gurley Precision Instruments, or GPI, is an ISO-9001 certified U.S. manufacturing company based in

Troy, New York Troy is a city in and the county seat of Rensselaer County, New York, United States. It is located on the western edge of the county, on the eastern bank of the Hudson River just northeast of the capital city of Albany, New York, Albany. At the ...

History

Gurley Enterprise was established by William Gurley and Lewis E. Gurley in 1845, brothers who were both alumni of

Rensselaer Polytechnic Institute Rensselaer Polytechnic Institute (; RPI) is a private university, private research university in Troy, New York, United States. It is the oldest technological university in the English-speaking world and the Western Hemisphere. It was establishe ...

. In 1885 Gurley started making Hydrologic equipment and in the early 1900s acquired many new fields including paper testing equipment and thermometers. During World War II Gurley won the Army-Navy ‘E’ Award for their contribution to the war effort. In the 1950s the company started producing optical encoders. During the Cold war era, Gurley manufactured

gyroscope A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining Orientation (geometry), orientation and angular velocity. It is a spinning wheel or disc in ...

sextant A sextant is a doubly reflecting navigation instrument that measures the angular distance between two visible objects. The primary use of a sextant is to measure the angle between an astronomical object and the horizon for the purposes of cel ...

star tracker A star tracker is an optical device that measures the positions of stars using photocells or a camera. As the positions of many stars have been measured by astronomers to a high degree of accuracy, a star tracker on a satellite or spacecraft may ...

theodolite A theodolite () is a precision optical instrument for measuring angles between designated visible points in the horizontal and vertical planes. The traditional use has been for land surveying, but it is also used extensively for building and ...

s, angle dividers, optical positioning systems, and various other precision guidance devices for

guided missiles A missile is an airborne ranged weapon capable of self-propelled flight aided usually by a propellant, jet engine or rocket motor. Historically, 'missile' referred to any projectile that is thrown, shot or propelled towards a target; this u ...

and for

space launch vehicle A launch vehicle is typically a rocket-powered vehicle designed to carry a payload (a crewed spacecraft or satellites) from Earth's surface or lower atmosphere to outer space. The most common form is the ballistic missile-shaped multist ...

s. Teledyne Corporation acquired W. & L. E. Gurley in 1968. In 1993 Gurley was sold again and became Gurley Precision Instruments. The W. & L. E. Gurley Building in Troy was named a

National Historic Landmark A National Historic Landmark (NHL) is a National Register of Historic Places property types, building, district, object, site, or structure that is officially recognized by the Federal government of the United States, United States government f ...

in 1983.

Units of measurement

GPI has been responsible for the creation of two commonly used units of measure. These units were so named due to the association with the devices used for their measurement.

Porosity

The Gurley second or Gurley unit is a unit that describes

air permeability Textile fibers, threads, yarns and fabrics are measured in a multiplicity of units. * A fiber, a single filament of natural material, such as cotton, linen or wool, or artificial material such as nylon, polyester, metal or mineral fiber, or huma ...

as a function of the time required for a specified amount of air to pass through a specified area of a separator under a specified pressure. Specifically, it is defined as the number of seconds required for 100 cubic centimeters (1 deciliter) of air to pass through 1.0 square inch of a given material at a pressure differential of 4.88 inches of water (0.176 psi)(ISO 5636-5:2003).

Stiffness

The Gurley unit is a measure of the stiffness of a material. Since the measurement device holds a piece of material vertically and tests the force required to deflect the material a given amount. One Gurley unit is equivalent to one milligram of force Handbook of nonwoven filter media (2007) p. 423 , however the Gurley unit also implies measurement with this apparatus. A related unit, the Taber, is highly correlated but uses a different apparatus (manufactured by Taber Industries) for performing measurements.

References

GPI homepageRelation between Taber and Gurley
Troy, New York Manufacturing companies based in New York (state) {{US-manufacturing-company-stub