Short definition
Ladder Logic (Ladder Diagram, LD) is a graphical programming language for PLC systems that simulates electrical circuit diagrams with contacts and coils. It visualizes control logic as horizontal circuits between two vertical busbars. Ladder Logic is standardized according to IEC 61131-3 and is the most widely used PLC programming language worldwide. It is used in membrane filtration systems for binary control tasks, interlocks, sequences and simple logic links, as it is intuitive and easy to maintain.
Functional principle
Ladder logic consists of networks (Rungs) that are evaluated from left to right. Input contacts (NO/NC) represent conditions, output coils represent actions. Logical AND operations are realized by series connection, OR operations by parallel connection. Timers, counters and comparators extend the functionality. The PLC processes the ladder programs cyclically. Modern development environments offer simulation, online testing and cross-referencing. The graphical display makes troubleshooting and documentation much easier.
Areas of application
Ladder Logic is particularly suitable for machine-related, binary control tasks in membrane filtration systems. It is the preferred language for electricians and commissioning engineers due to its proximity to conventional circuit diagrams. Complex interlocking logic and safety functions are displayed transparently and comprehensibly. Its widespread use ensures the availability of know-how and easy maintenance.
Typical areas of application:
- Pump and valve controls with interlocks
- Sequence control of CIP phases
- Safety logic for emergency stop and protective functions
- Binary on/off logic for auxiliary processes
- Limit value monitoring and alarms
Summary
Ladder Logic is the most established and intuitive programming language for industrial control systems with a high level of acceptance among maintenance personnel. It enables fast programming, simple troubleshooting and transparent documentation. For plant engineers, it means standardized engineering with a broad knowledge base and long-term maintainable control programs in membrane filtration plants.
DE_DE 
EN 