Definition of Ladder Logic

Ladder logic was initially developed as the method of documenting the construction and design of relay racks as they were used in the field of process controlling and manufacturing. It later developed into a programming language that depicts the program in terms of a graphical diagram which is taken from the circuit diagrams of the hardware of relay logic.

The basic use of this language is the development of the software associated with the programmable logic controllers (PLCs) that are a part of applications of industrial control.


Ladder logic originated as a method of representing construction and design of relay racks. Each of the devices included in the rack was represented in the ladder diagram with the help of a symbol, it also included the external items, including the chillers and the pumps, which were a part of the system. The purpose behind the use of these diagrams was to facilitate the replication of the relay rack systems at a different location or at the same location on a different date.

With the advancements in the technology, the conventional relay racks were replaced by PLC. This was accompanied by the evolution of the previous ladder diagrams into a functional programming language, which is referred to as ladder logic in the present era. The purpose behind the deployment of ladder diagrams as the foundation stone of the new programming language can be declared as practical.

This is because it was something that the programmers and technicians already new. As a result, ladder logic did not accompany huge training costs like other programming languages.

The best use of notation of ladder logic notation can be made in systems that require binary values. This increases the functionality of the language and enable the technicians to avoid unnecessary complications. Such programs are commonly used for security purposes.

The development of ladder language stemmed from the replacement of relay racks by the PLCs. The language is one of the most commonly used languages in the area of industry control applications and has provided the technicians with a means of managing their processes in a more effective manner.

The Ladder logic programs associated with PLCs can be very powerful and robust, due to the high functionality and careful development and evolution of the language. These programs, therefore, come with an ability of efficiently controlling the complex and technical industrial processes.

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