Beckman fixed fragile pH electrodes by amplifying the signal, not the glass

By the mid-1930s, chemists measuring acidity relied mostly on litmus paper — cheap, but useless for citrus processors, since the sulfur dioxide used to preserve lemon juice bleached out the litmus color change entirely. The alternative, a glass electrode connected to a sensitive galvanometer, measured pH electrochemically and worked in principle, but in practice the glass electrodes that chemist Glen Joseph tried at the California Fruit Growers Exchange broke constantly.

The reason was built into how the existing instruments worked: the available galvanometers had poor electrical sensitivity, so getting a strong enough signal for them to register meant using a glass electrode thin and large enough to keep its electrical resistance low — and thin, large glass under lab conditions was fragile glass. Chemists trying to make the measurement more reliable kept running into the same trade-off: a sturdier electrode produced too weak a signal for the meter to read, and a signal strong enough to read required an electrode too delicate to survive routine handling.

Replaced the galvanometer with a vacuum tube amplifier that could read a weaker signal, so the electrode could be built rugged instead of thin and delicate.

The galvanometer's poor sensitivity forced electrodes to be thin and large to lower resistance, causing breakage.

A vacuum tube amplifier could detect and boost much weaker signals, removing the need for fragile electrodes.

Integrating amplifier, electrode, and meter made the instrument easy for any chemist to use, driving adoption.

When a sensor must be fragile to satisfy a weak detector, improve the detector to accept a sturdier sensor's weaker signal.

The resulting "acidimeter," soon renamed the pH meter, used a newly developed, far more rugged glass electrode paired with vacuum tube amplification, solving Joseph's original fragility problem outright. Beckman's company, National Technical Laboratories, sold 444 units in 1936, its first full year, and by 1939 had sold nearly 2,000, appearing in the catalogs of every major US scientific instrument dealer.