How do you choose an S7-1200 G2 for a new machine?

For the described machine, both S7-1200 generations are candidates because the logic is modest and does not call for heavy process control or advanced motion; select between them only after checking exact module fit, cabinet dimensions, and engineering-software requirements. Treat the second-generation S7-1200 (G2) as a new hardware selection, not an automatic drop-in replacement for a first-generation unit.

Define the machine requirements before choosing a CPU

Start with the machine’s actual I/O, control functions, communications, and planned expansion. The stated application does not need an S7-1500 for processing or motion demands, but that alone does not settle the choice: installed cost, commonality with other machines, expansion plans, and panel constraints can make the larger family the better project decision.

List each required signal and module, then record any functions that depend on a particular module or software library. Separate requirements for the first machine from likely future additions. A CPU that handles the present logic can still be a poor fit if a needed module is unavailable in the selected generation or the design cannot accommodate later expansion.

1. Record required I/O and identify the modules each signal requires.
2. List any existing libraries, standards, or machine designs that the new program must reuse.
3. Write down the panel’s available width, height, wiring-duct clearance, and intended expansion space.

Check 1: The requirement list names a supported hardware configuration for every required signal and function; unresolved module or library dependencies remain explicit before ordering.

Compare the first-generation and G2 S7-1200

The selection question is not simply whether G2 is faster. The information presented describes G2 as faster, with more memory and lower cost than first-generation S7-1200 hardware, but gives no CPU models, measured scan times, memory figures, prices, or benchmark workload. Do not convert those broad comparisons into a performance guarantee for the machine. Request the exact CPU data and compare it against the application’s measured or estimated task load.

For a modest machine, the useful question is whether either CPU meets the required response and memory needs with enough margin for the program and planned additions. If performance is not a constraint, prioritize module compatibility, engineering environment, cabinet fit, and total system cost. If performance or memory could become limiting, compare exact selected CPU specifications and test representative program behavior rather than relying on the generation label.

Decision factor	First-generation S7-1200	S7-1200 G2
Performance and memory	Use the selected CPU’s specifications and workload test.	Reported as faster and with more memory; verify against exact CPU data.
Module coverage	Reported as having a broader current module range than G2.	Reported as having roughly 90% of first-generation modules; verify every required catalog item.
Price	Reported as costing more than G2 in the comparison.	Reported as costing less; obtain current project quotations.
Panel fit	Compare actual dimensions with the existing or planned panel.	Reported as narrower but taller; confirm exact dimensional drawings.

Check 2: The selected CPU meets the application’s documented performance and memory needs, and the decision record cites exact model data rather than an unquantified generation comparison.

Confirm that every required module is available

Module coverage is the main product-range risk identified for G2. The reported estimate is that G2 has about 90% of the modules available for the first generation; treat that as a prompt to check the actual project BOM, not as a complete compatibility list. Availability of most modules is not enough if one required I/O or communication module is missing.

Check the exact module order identifiers, CPU compatibility, and availability for the planned build date with current product documentation and the distributor. Make the comparison module by module. If an existing library or program references first-generation hardware, check whether the required hardware configuration and associated functions can be used with the proposed G2 configuration. The claim that G2 has improved compatibility with existing libraries is a perception in the supplied information, not a substitute for testing the actual project.

1. Build the required module list from the I/O schedule and machine architecture.
2. Confirm each module is offered for the selected generation and can be configured with the selected CPU.
3. Open or migrate a representative project and resolve hardware and library dependencies before committing the design.
4. Record any unavailable module, replacement, or change to the machine design as a selection issue.

Check 3: Every required module appears in the confirmed configuration for the selected generation, and the engineering project accepts the planned hardware and library content without unresolved dependencies.

Check panel dimensions and terminal suitability

A change in installation footprint means a change in physical mounting dimensions, not just a different CPU performance level. G2 was described as narrower and taller than first-generation hardware. In a new panel, compare the exact drawing with the available mounting area. In an upgrade, also inspect the wiring ducts and cable paths: a taller unit can conflict with existing ducting even when its width is reduced.

Terminal quality was raised as a concern, but no measurement, failure mode, or specific terminal defect was provided. Evaluate the exact hardware in the intended wiring conditions rather than treating the broad comment as a proven defect. Review the terminal arrangement and conductor access, and inspect a sample or approved drawing where the installation has restricted access or frequent wiring changes. If the terminals do not suit the machine’s wiring plan, compare an alternative architecture before panel fabrication.

1. Obtain dimensioned drawings for the exact CPU and module arrangement.
2. Check clearances against the panel layout, including wiring ducts and cable routing.
3. Review the terminal arrangement against the specified conductors and assembly method.

Check 4: The selected assembly fits the available panel envelope with duct and wiring access preserved, and the terminal arrangement matches the documented wiring plan.

Resolve TIA Portal and license requirements

The supplied information places G2 support in a relatively new TIA Portal release, with versions 20 or 21 suggested uncertainly. It also states that G2 uses the same STEP 7 Basic license as first-generation S7-1200 hardware. Verify both points against the exact CPU, current compatibility information, and the software installation planned for the project. Do not schedule commissioning around an unverified version estimate.

Before purchase, confirm the minimum TIA Portal version that supports the selected hardware, whether the team can install and use that release, and whether the available license covers the required configuration and programming work. If an older project or shared engineering workstation must remain in use, check whether G2 creates a version conflict. Resolve that dependency before building libraries, committing a project file, or delivering the machine.

1. Identify the exact CPU and modules under consideration.
2. Confirm their support in the TIA Portal version available to the engineering team.
3. Confirm the applicable STEP 7 Basic license and any project workflow constraints.
4. Create and compile a small test project using the intended configuration and workstation.

Check 5: The engineering workstation recognizes the selected hardware in the planned TIA Portal release, and the project compiles under the license available for commissioning.

Compare the complete machine cost with S7-1500 alternatives

CPU price alone does not determine the most economical architecture. One comparison in the supplied information puts the low-end S7-1200 and low-end S7-1500 price difference at about 600 EUR, while also arguing that expansion, standardization, and familiarity can justify an S7-1500 on a larger machine project. That price is a reported comparison, not a current quotation; use distributor pricing for the specific bill of materials.

For a very small machine, the source gives roughly ten I/O as an example where S7-1200 cost can be decisive, especially when the machine is built in quantity. For a one-off or expandable machine, compare the PLC and I/O, engineering reuse, future expansion, panel changes, and commissioning effort as one system. The S7-1511 and S7-1511F were suggested as alternatives, and S7-1510SP with ET200SP I/O was also suggested. These are options to evaluate, not automatic upgrades: select a safety-capable CPU only when the machine’s safety design requires it.

Project condition	Selection direction	Decision to verify
Very small, cost-sensitive machine or high-volume build	Consider S7-1200.	Confirm the complete CPU and I/O configuration meets requirements at quoted cost.
Expansion, commonality, or standardization has high value	Compare S7-1500, including S7-1511 or S7-1511F where appropriate.	Compare lifecycle and integration value against the complete S7-1200 solution.
Distributed I/O or an alternate compact architecture is under consideration	Evaluate S7-1510SP with ET200SP I/O.	Validate the architecture, modules, layout, and project requirements before redesign.

Check 6: The selected architecture wins on a documented system comparison that includes current quotes, required I/O, expansion needs, and the engineering environment—not CPU purchase price alone.

Complete the end-to-end selection verification

Close the selection by testing the proposed hardware and software as one configuration. This catches the failure pattern in which a CPU is selected first and module coverage, dimensions, or engineering compatibility is checked only after panel or program work has begun. Keep the configuration record tied to the exact CPU, modules, drawings, and software release used for the decision.

1. Freeze the proposed CPU and I/O bill of materials.
2. Check all I/O points against the selected modules and confirm no required module is missing.
3. Confirm the dimensions and terminal arrangement against the panel and wiring design.
4. Open, configure, and compile a representative project in the intended TIA Portal environment with the available license.
5. Compare the quoted system cost and expansion plan against the considered S7-1200, G2, and S7-1500 options.

Check 7: Release the design only when the BOM, project configuration, software environment, panel layout, and cost comparison all describe the same selected system.

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