Pocket comparator

A pocket comparator is an optical device for measuring and inspection comprising a loupe and a reticle.[1] The instrument was developed and manufactured by the Bell & Howell Company, but similar instruments of other names are made by other manufacturers.[2][3]

Reticle of Bell & Howell Pocket Comparator
Bell & Howell Pocket Comparator

It is used for:

  • Linear measurements in fractions of an inch.[4][5][6]
  • Circular measurements in fractions of an inch.
  • Radius measurements.
  • Angle measurements.
  • Narrow line width measurements.[7]
  • Circular measurements in decimals of an inch.
  • Linear measurements in inches.
  • Linear measurements in millimeters

Measurements are performed by bringing the surface of the reticle as close as possible to the work inspected.

[8]

References
  1. "The Pocket Comparator - A New Optical Measuring Instrument". in: Electrical Engineering (Volume 69, Issue 3, p. 220) March 1950 http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6433729&url=http%3A%2F%2Fieeexplore.ieee.org%2Fstamp%2Fstamp.jsp%3Ftp%3D%26arnumber%3D6433729
  2. " by Marcus Bowman Crowood, 31 August 2015, Crafts & Hobbies
  3. "Low price measuring magnifier uses real glass reticle", Journal of the Franklin Institute, 1955, Vol. 259(6), pp. 516–516 [peer reviewed journal]
  4. Charles C. Ryerson and Anthony J. Gow: Ship Superstructure Icing: Crystalline and Physical Properties in: US Army Corps of Engineers® Engineer Research and Development Center (August 2000) p. 14
  5. van Altena, W. F., Low-luminosity members of the Hyades cluster. Astronomical Journal, Vol. 71, p. 482–512 (1966)
  6. I. B. A. Menown, G. MacKenzie and A. A. J. Adgey, Optimizing the initial 12-lead electrocardiographic diagnosis of acute myocardial infarction, European Heart Journal (2000) 21, 275–283
  7. DEPARTMENT OF THE ARMY EM 1110-2-2002 U.S. Army Corps of Engineers: EVALUATION AND REPAIR OF CONCRETE STRUCTURES p.2-11 http://www.publications.usace.army.mil/Portals/76/Publications/EngineerManuals/EM_1110-2-2002.pdf
  8. The Pocket Comparator: A New Measuring Instrument, in: INDUSTRIAL QUALITY CONTROL VOL.6 NO.5, March 1950 pp. 22-23
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