The diagram is annotated in red and blue ink, indicating first and second position.
Arnold Beckman invented his first pH meter in 1934 at the request of a chemist from the California citrus industry, who needed an accurate way to measure the acidity of his product. The resulting instrument kicked off rapid development not only of Beckman Instruments, Inc. but also of the electronic scientific instrument industry.
|Place of creation|
“Circuit Diagram, Beckman PH Meter, Laboratory Model,” January 24, 1945. Beckman Historical Collection, Box 18, Folder 26. Science History Institute. Philadelphia. https://digital.sciencehistory.org/works/r781wg491.
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