ABSTRACT
In a programmed control system, the control point is automatically adjusted to follow a predetermined pattern with respect to time and process conditions. The cam-operated, programmed controller offers the advantages of simplicity and ease of operation. The limitations are that it is only a single loop; and a program change requires a new cam layout, and, in some cases, a change in cam speed. A digital computer-oriented system provides versatile, preprogrammed sequential logic control functions. It is used to automate adjustments of analog set points and the check and inhibit actions of interlock logic. Elementary mathematical manipulations (addition, subtraction, multiplication, division) can be performed within a step of the logic program. Each of the stepped phases of all operational events is controlled by input contacts and feedback. The programmable controller is a solid-state, sequential logic control system. It replaces mechanical logic equipment, such as relays, stepping switches, and drum programmers.
