February 8, 2019

Industrial automation has been well underway for decades, with the birth of modern industrial engineering and computers forever changing the manufacturing landscape as early as the 1950s. The Programmable Logic Controller, or PLC, is one of the single most impactful pieces of industrial technology to result out of what is now known as the third industrial revolution – a pretty impressive feat given that the 1950s and 60s also brought about the birth of mainframe computing, personal computers, semiconductors and more.

PLCs have been around since 1968; however, as the world marches on into the fourth industrial revolution (also known as Industry 4.0), they continue to be a bedrock of industrial automation. Today, Rockwell’s Allen Bradley and Siemens are two PLC giants and are widely used around the world. Here’s an overview of how they stack up.

Performance and Usability

PLC Driver control box

When comparing Allen Bradley and Siemens’ PLCs in terms of performance, both are relatively similar in that their speed, reliability and output are just about evenly matched. The main difference rather lies in how each can be operated and integrated into a particular industrial setting.

Allen Bradley PLCs boast a known user-friendly interface, which makes them an easier point of entry for manufacturing workers looking to learn a PLC system. A relatively untried PLC technician without extensive programming experience can still make use of an Allen Bradley PLC with relative ease. Debugging an Allen Bradley typically also takes less time and effort than when it comes to doing the same with a Siemens PLC. An Allen Bradley PLC may also be of interest to manufacturers looking for connectivity as a feature; these PLCs can easily connect with third parties, allowing information to be easily imported and exported from Excel, SCADA databases and more.

All that said, ease of use isn’t necessarily the winning factor when it comes to choosing a PLC. Siemens allows for their PLCs to be heavily programmed and customized to suit particular business needs. Naturally, this implies that a more robust computer programming background will be needed in order for a technician to effectively make use of and maintain a Siemens PLC.

high technology industrial machine control by PLC


While Allen Bradley PLCs may be the winner when it comes to overall ease-of-use, in terms of hardware and installation they require a little extra touch, whereas a Siemens PLC can be plugged into most standard 24V DC power supplies. Allen Bradley requires users to also have on hand an Allen Bradley Rack and an Allen Bradley power supply. As far as safety ports go, Siemens PLCs come with built-in protocols that meet European standards (ASI, Profinet, Profibus) whereas Allen Bradley PLCs come with American protocols (EthernetIP, ControlNet, DeviceNet, etc.).


Support availability is an important feature to consider when purchasing a PLC. Siemens will offer 24/7 post-sales technical support, field service and spare parts every day of the year, for a number of different products including anything that falls under their Process & Factory Automation category. Rockwell also offers 24/7 technical support for with 365-day availability. but is less comprehensive than what Siemens offers and the level of free support is dependent upon the amount of hardware installed.

electrical terminal in junction box

Which is the winner?

While it might be tempting to choose a PLC based on support availability and cost, ultimately, it’s more important to pick the right tool for the job. Of course, given that a one-size-fits-all approach is rarely ideal, there’s no reason why both these automation systems could not exchange communications and be made to work effectively together if need be. As such, there’s no true “winner” when comparing the two brands.

Even in terms of sheer popularity, the “winner” actually depends on where you work. Siemens PLCs are hands-down the most popular of the two in Europe, where Siemens AG also happens to be the largest industrial manufacturing company on the continent. In North America, Rockwell Automation’s Allen Bradley is by far the more popular PLC provider.

Learn more about factory automation via Rockwell PLCs by checking out George Brown’s PLC technician training program.


Hello guys, Do you have a plan to create Siemens PLC online training course? Best regards, Eugene.

We do offer two online PLC programs; a foundation and advanced program with simulation software that emulates the Rockwell (Allen-Bradley) RSLogix 500 and 5000 series . At this point in time we do not plan to add another PLC program.

I would like to have more training on plc issue gavin

Thanks Gavin, I will have a Program Consultant contact you directly.

We will email an information package shortly. Or you can contact a Program Consultant toll-free at 1-888-553-5333.

I have some experience with altering and making Allen Bradley ladder logic programs but more than experience dealing with Siemens communication equipment. I was wondering what are some of the terminology differences between the two for inputs/outputs, digital and analog.

Common PLC input/output (I/O) can be analog and/or digital. An analog signal is one whose value continually varies over time. They are best represented as a continuous signal like a sine wave. ... By contrast, a digital (or discrete) signal is one with a value at a specified interval of time. For further help please contact our Program Consultant toll-free at 1-888-553-5333.

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