Region can play a role in choice of programming language. Anecdotally, structured text (ST) is more popular in Europe, whereas ladder diagram (LD) rules in the United States. “Companies on the west coast near tech hubs like San Francisco often prefer structured text. Within industries, pharmaceutical and food and beverage are more likely to use function block diagram (FBD), as that was often the language of choice in distributed control system (DCS) and process solutions for those industries,” says Patrick Smith, senior project engineer at DMC, a CSIA-certified system integrator.
Ladder diagram remains strong in the central and Midwest regions of the United States, particularly in the rust belt, among automotive manufacturers. “There is a noticeable shift toward increased use of ST and FBD,” says Tim Hider, industry marketing manager for smart manufacturing and digital solutions at Mitsubishi Electric Automation. “Coastal regions, home to industries like semiconductors, data centers and pharmaceuticals, tend to favor ST due to the workforce’s familiarity with high-level programming languages. Function block diagram is also gaining popularity, particularly among original equipment manufacturers (OEMs) involved in motion control, as it provides a comprehensive visual overview of servo operations on a single screen.”
Engineering disciplines can sometimes dictate a programming-language preference for programmable logic controllers (PLCs), as well.
“Programmers with an electrical engineering background often tend to prefer ladder diagram, as it closely resembles electrical schematics that contain contacts, relays and coils++,” says Imran Mohamed, motion control application engineer at Yaskawa America. “In contrast, those with a computer engineering background typically prefer structured text, due to its similarity to high-level programming languages like C or C.”
Hoat Phung, senior application engineer at ABB says ladder diagram is still dominant with the company’s U.S.-based customers. “But with the younger engineers moving into this field, they have a tendency to use a little bit more of a mixture of structured text and function block diagram,” he adds.
Structured text is dominant in Germany and Europe, says Phung, “but in the United States, we still have electricians in the factories maintaining the machinery, so ladder diagram is still the backbone because that’s what they are familiar with.”
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Michael Guckes, product manager at Hottinger Brüel & Kjær (HBK), a machine builder headquartered in Virum, Denmark, says the company’s software developers prefer modern object-oriented structured text. Largely, the company’s younger engineers prefer object-oriented languages.
HBK focuses on test-and-measurement machines and systems, which often require precise timing, data logging and signal conditioning. To do this, HBK uses hardware that interfaces with operational technology (OT) and information technology (IT) assets.
IEC 61131-3 languages support real-time controls on the OT side. Ethernet and TCP/IP are used for data logging and analysis by IT.
HBK production engineers set up and program its calibration machines, and a separate engineering department, called system solutions, programs code for customers. It sees a growing need for more advanced or modular programming approaches, like ST, again, strongly supported by young engineers, Guckes says.
Most of the controls systems for HBK machines are “sequence-driven,” Guckes says. “They follow the calibration-procedure for our sensors. In case of an unexpected event or failure, a watchdog function saves the machines and sensors from damage.”
For high-precision test environments, more libraries dedicated to measuring tasks would be helpful for IEC 61131-3 programming languages, he adds, taking into account the needs of adjusting and managing measurement amplifiers. “It would help a lot to offer databases to handle bigger amounts of measurement data,” Guckes says.
