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

Troy, New York Troy is a city in the U.S. state of New York and the county seat of Rensselaer County. The city is located on the western edge of Rensselaer County and on the eastern bank of the Hudson River. Troy has close ties to the nearby cities of Albany ...

History

Gurley Enterprise was established by William Gurley and Lewis E. Gurley in 1845, brothers who were both alumni of Rensselaer Polytechnic Institute. 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 The Cold War is a term commonly used to refer to a period of Geopolitics, geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc. The term ''Cold war (term), co ...

, Gurley manufactured gyroscopes, sextants,

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 an ...

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

guided missiles In military terminology, a missile is a guided airborne ranged weapon capable of self-propelled flight usually by a jet engine or rocket motor. Missiles are thus also called guided missiles or guided rockets (when a previously unguided rocket i ...

and for

space launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pads, supported by a launch control center and syste ...

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 building, district, object, site, or structure that is officially recognized by the United States government for its outstanding historical significance. Only some 2,500 (~3%) of over 90,000 places listed ...

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 man-m ...

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