While a professor at California Institute of Technology, he founded Beckman Instruments based on his 1934 invention of the pH meter, a device for measuring acidity (and alkalinity), later considered to have "revolutionized the study of chemistry and biology".

[3]: 17–18  While still in high school, Arnold started his own business, "Bloomington Research Laboratories", doing analytic chemistry for the local gas company.

After three months at marine boot camp on Parris Island, South Carolina,[3]: 31  he was sent to the Brooklyn Navy Yard, for transit to the war in Europe.

Working with Walter A. Shewhart,[3]: 61  Beckman developed quality control programs for the manufacture of vacuum tubes and learned about circuit design.

After receiving a Ph.D. in photochemistry in 1928[5] for this application of quantum theory to chemical reactions, Beckman was asked to stay on at Caltech as an instructor and then as a professor.

He started the National Inking Appliance Company, obtaining space in a garage owned by instrument maker Fred Henson and hiring two Caltech students, Robert Barton and Henry Fracker.

Sunkist needed to know the acidity of the product at any given time, and the colorimetric methods then in use, such as readings from litmus paper, did not work well because sulfur dioxide interfered with them.

Beckman, familiar with glassblowing, electricity, and chemistry, suggested a design for a vacuum-tube amplifier and ended up building a working apparatus for Joseph.

The glass electrode used to measure pH was placed in a grid circuit in the vacuum tube, producing an amplified signal which could then be read by an electronic meter.

Although it was priced expensively at $195, roughly the starting monthly wage for a chemistry professor at that time, it was significantly cheaper than the estimated cost of building a comparable instrument from individual components, about $500.

On April 8, 1935, Beckman renamed his company National Technical Laboratories, formally acknowledging his new focus on the making of scientific instruments.

[3]: 151  With Beckman's model D, later known as the DU spectrophotometer, National Technical Laboratories successfully provided the first easy-to-use single instrument containing both the optical and electronic components needed for ultraviolet-absorption spectrophotometry.

[3]: 156 Beckman's DU spectrophotometer has been referred to as the "model T" of scientific instruments: "This device forever simplified and streamlined chemical analysis, by allowing researchers to perform a 99.9% accurate quantitative measurement of a substance within minutes, as opposed to the weeks required previously for results of only 25% accuracy.

Beckman was approached by the Office of Rubber Reserve about developing an infrared spectrophotometer to aid in the study of chemicals such as toluene and butadiene.

The Office of Rubber Reserve met secretly in Detroit with Robert Brattain of the Shell Development Company, Arnold O. Beckman, and R. Bowling Barnes of American Cyanamid.

The lab was part of a secret network of research institutions in both the United States and Britain that were working to develop radar, "radio detecting and ranging".

Nonetheless, for use in continuously moving airplanes, ships, or submarines, which might be under attack, a redesign would be needed to ensure that the knobs could withstand shocks and vibrations.

Originally approached to supply housing boxes for the meter by Holmes Sturdivant, Pauling's assistant, Beckman was soon asked to produce the entire instrument.

While the board of National Technical Laboratories was unwilling to support the secret project, whose details they could not be told, they agreed that Beckman was free to follow up on it independently.

Scientists in the project were attempting to develop instruments to measure radiation in gas-filled, electrically charged ionization chambers in nuclear reactors.

Beckman realized that with a relatively minor adjustment – substituting an input-load resistor for the glass electrode – the pH meter could be adapted to do the job.

First characterized as "gas attacks" in 1943, suspicion fell on a variety of possible causes including the smudge pots used by orange growers, the smoke produced by local industrial plants, and car exhausts.

The Los Angeles Chamber of Commerce was one of the organizations concerned about the possible causes and effects of smog, as it related both to industry (and jobs) and to quality of life in the area.

[19] They developed an apparatus to collect particulate matter from Los Angeles air, using a system of tubing intermittently cooled by liquid nitrogen.

[3]: 224–226 Beckman himself was approached by California governor Goodwin Knight to head a Special Committee on Air Pollution, to propose ways to combat smog.

[3]: 207–208  Liston developed instruments to measure smog and car exhaust emissions, essential to attempts to improve Los Angeles air quality in the 1950s.

He identified the two key issues of his term as battling smog, and supporting the collaboration of local science, technology, industry, and education.

The firm launched in February 1956, the same year that Shockley received the Nobel Prize in Physics along with John Bardeen and Walter Houser Brattain "for their researches on semiconductors and their discovery of the transistor effect".

Moreover, he decided that the lab would research an invention of his own, the four-layer diode, rather than developing the diffused silicon transistor that he and Beckman had agreed upon.

[21] In 1957, eight leading scientists including Gordon Moore and Robert Noyce left Shockley's group to form a competing startup, Fairchild Semiconductor, which would successfully develop silicon transistors.