The Early Development of Electronic pH Meters

Abstract

This paper describes the early development of electronic pH meters, starting with the work of Kenneth Goode in the early 1920s, and the subsequent rapid development of electron tube technology and of more efficient pH-measuring circuits, culminating about a decade later in the production of commercially successful electronic pH meters by Cambridge Instruments, Beckman, Radiometer, and others.These early, commercially successful pH meters were nullbalance instruments requiring manual adjustments of potentiometers. The subsequent development of stable dc amplifier circuits, first with vacuum tube technology, and then with solid state electronics, led to the present availability of inexpensive yet sufficiently accurate direct-reading pH meters. These modern instruments take after the original designs of Goode, who envisioned, designed, and patented the pH meter as a directreading instrument.