# Gurley Precision Instruments

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{{Infobox company
| name             = Gurley Precision Instruments
| logo             = 
| caption          = 
| type             = [Private](/source/Privately_held_company)
| predecessor      = Gurley Enterprise
| foundation       = 1845
| founder          = [William Gurley](/source/William_Gurley) and Lewis E. Gurley
| defunct          = 
| location_city    = 
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| location         = [Troy, New York](/source/Troy%2C_New_York)
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| key_people       = 
| industry         = manufacturing
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}}
'''Gurley Precision Instruments''', or '''GPI''', is an ISO-9001 certified U.S. manufacturing company based in [Troy, New York](/source/Troy%2C_New_York).

==History==
Gurley Enterprise was established by [William Gurley](/source/William_Gurley) and Lewis E. Gurley in 1845, brothers who were both alumni of [Rensselaer Polytechnic Institute](/source/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](/source/Army-Navy_%E2%80%98E%E2%80%99_Award) for their contribution to the war effort. In the 1950s the company started producing optical encoders. During the [Cold war era](/source/Cold_war_era), Gurley manufactured [gyroscope](/source/gyroscope)s, [sextant](/source/sextant)s, [star tracker](/source/star_tracker)s, [theodolite](/source/theodolite)s, angle dividers, optical positioning systems, and various other precision guidance devices for [guided missiles](/source/guided_missiles) and for [space launch vehicle](/source/space_launch_vehicle)s.<ref>[https://archive.org/stream/Aviation_Week_1963-07-22#page/n56/mode/2up Gurley’s Unisec—heart of the Apollo Project’s Space Sextant]. // ''Aviation Week & Space Technology'', July 22, 1963, v. 79, no. 4, p. 113.</ref> [Teledyne Corporation](/source/Teledyne_Technologies) acquired W. & L. E. Gurley in 1968. In 1993 Gurley was sold again and became Gurley Precision Instruments.

The [W. & L. E. Gurley Building](/source/W._%26_L._E._Gurley_Building) in Troy was named a [National Historic Landmark](/source/National_Historic_Landmark) 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](/source/air_permeability) 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&nbsp;inches of water (0.176 psi)(ISO 5636-5:2003).<ref>Handbook of nonwoven filter media (2007) p. 248</ref>

===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<ref>
Handbook of nonwoven filter media (2007) p. 423</ref>
, however the Gurley unit also implies measurement with this apparatus.  A related unit, the [Taber](/source/Taber_Industries), is highly correlated but uses a different apparatus (manufactured by [Taber Industries](/source/Taber_Industries)) for performing measurements.

==References==
{{Reflist}}
{{cite book
|last=Hutten
|first=Irwin Marshall
|title=Handbook of nonwoven filter media
|url=https://books.google.com/books?id=RzYgBHumVdoC
|edition=illustrated
|year=2007
|publisher=Elsevier
|isbn=978-1-85617-441-1
|ref=hnfm
}} 
*[http://gurley.com/ GPI homepage]
*[http://www.unc.edu/~rowlett/units/dictP.html#porosity A Dictionary of Units of Measurement]
*[http://www.tappi.org/s_tappi/doc.asp?CID=107&DID=524570#Q4 Relation between Taber and Gurley] {{Webarchive|url=https://web.archive.org/web/20070108184758/http://www.tappi.org/s_tappi/doc.asp?CID=107&DID=524570#Q4 |date=2007-01-08 }}

Category:Troy, New York
Category:Manufacturing companies based in New York (state)

{{US-manufacturing-company-stub}}

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Adapted from the Wikipedia article [Gurley Precision Instruments](https://en.wikipedia.org/wiki/Gurley_Precision_Instruments) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Gurley_Precision_Instruments?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.