Gurley Precision Instruments

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

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 1900’s acquired many new fields including paper testing equipment and thermometers. During World War II Gurley won the Army-Navy E awards for their contribution to the war effort. In the 1950’s the company started producing optical encoders. Teledyne corporation acquired W. & L. E. Gurley in 1968. In 1993 Gurley was sold again and became Gurley Precision Instruments.

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 describing 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 given pressure differential.

Stiffness

The Gurley unit is a measure of the stiffness of a material. 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 on milligram of force, 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 homepage
• A Dictionary of Units of Measurement
• Relation between Taber and Gurley