An Early On-Line Process Computer-Controller

Prior to 1938, the only method to determine optimum operation of an oil cracking still was by sampling at selected points and subsequent laboratory analysis of the fluid samples. This analysis so delayed the results that the information was called "history instead of news." The author designed a process analog computer, using six cascaded Wheatstone bridges, which successfully solved an empirical equation within 12 s, thereby making control of the still possible from current instrument readings.