Perrygraf Ohm's Law Calculator Slide Rule for Ohmite
date: label: date made
content: 1941
name: label: maker
content: Perry Graf Corporation
notes: label: Description
content: This rectangular yellow, orange, black, and white rule consists of a paper envelope holding a paper slide, held together with metal rivets. The Ohmite Manufacturing Company of Chicago commissioned it from the Perrygraf (or Perry Graf) Corporation of Maywood, Ill.
label: Description
content: Lester E. Perry (1901–1991), a machinery inspector in Cook County, Ill., founded Perrygraf in 1934. He and his associates, including his relative Oscar Perry, designed and manufactured special-purpose "slide charts." By 1960, the firm had a branch in California and a plant in Puerto Rico. In 1968 the firm was sold to Nashua Corporation, and operations in Illinois ceased. Some former employees started their own slide chart companies. James E. Johnson, the former plant manager, established American Slide Chart in 1971. This Wheaton, Ill., firm became sufficiently successful to purchase Perrygraf in 1988. Another former Perrygraf employee and engineer established Datalizer Slide Charts of Addison, Ill. Both American Slide Chart/Perrygraf and Datalizer Slide Charts remain in business as of 2012.
label: Description
content: The Ohmite Manufacturing Company, established in 1925, sold rheostats, fixed resistors, and adjustable resistors. Its Ohm's Law Calculator had scales that allowed the user to find ohms, volts, amperes, and watts, given any two of those measures. It also had a chart for finding the stock number of desired parts. This example was copyrighted in 1941 and sold for ten cents. The name of the donor is stamped on both sides. An electronic version of the calculator may be found on the company's website.
label: Description
content: References: George Melloan, "Pocket Slide Charts Aid Engineers, Help Sell Steel, Lipstick," <i>Wall Street Journal</i>, September 4, 1953, 1; Display Ad, <i>Los Angeles Times</i>, November 8, 1960, 22; "About Perrygraf," http://www.quinndesign.com/profweb/perrygraf/; "About Us," <i>American Slide Chart/Perrygraf</i>, http://www.americanslidechart.com/aboutus.html; "Slide Chart Specialists," <i>Datalizer Slide Charts</i>, http://www.datalizer.com/about-us/; "Ohmite History," http://www.ohmite.com/history.php.
label: Location
content: Currently not on view
topic: label: Subject
content: Mathematics
label: Subject
content: Rule, Calculating
label: Subject
content: electricity
label: Subject
content: Engineering, Electrical
setName: label: See more items in
content: Medicine and Science: Mathematics
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content: Science & Mathematics
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content: Slide Rules
creditLine: label: Credit Line
content: Gift of Oscar W. Richards
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: 1979.3074.03
label: nonaccession number
content: 1979.3074
label: catalog number
content: 1979.3074.03
objectType: label: Object Name
content: calculating rule
label: Object Name
content: slide rule
physicalDescription: label: Physical Description
content: paper (overall material)
label: Measurements
content: overall: .3 cm x 23.5 cm x 10.6 cm; 1/8 in x 9 1/4 in x 4 3/16 in