An unidentified man kneels in a field of crops looking at the reading on a Pocket pH Meter, first marketed by Beckman Instruments in 1956. A photograph from the same session appears in advertisements for the Pocket pH Meter.

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.