How to identify a PLC CPU from its nameplate

Start with the complete article number exactly as it appears on the visible product marking. For the two Siemens examples in this guide, the manufacturer's product data names that field "Article number" and separately names the product type. Keep those as two fields in your notes instead of blending a family label into the identifier.

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The flow stops before cabinet access or equipment contact. It describes evidence capture, not electrical work.

Work only from a location that your site's safety procedure allows. Do not open an energized cabinet, reach past guards, clean a label, disconnect wiring, or remove a module for a photograph. Siemens limits cabinet access to authorized personnel and requires power to the S7-1200 and related equipment to be disabled before installation or removal.

Take a straight, readable photograph only when that can be done safely and without touching the equipment. Then transcribe the complete article number, preserving every letter, digit, and hyphen. A maintenance note that says only "1214C" can help locate a record, but it does not identify either exact article used in the comparison below.

Copy any other visible version or serial marking into its own field and label the source as a photograph. Do not fill an unreadable character from memory or from a current catalog page. A current product record describes the catalog article; it is not evidence of every marking or software state on the installed unit in front of you.

Treat 6ES7214-1AG40-0XB0 as one exact Siemens article number, not as a four-block decoding exercise. The official product record identifies that complete string as a CPU 1214C DC/DC/DC. The source does not provide the claimed four-block grammar, so this guide does not assign a meaning to 0XB0 or to each visual group of characters.

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Character grouping is used only to check the transcription. The exact Siemens record, not an inferred code grammar, supplies the specifications.

For transcription, you may compare short runs of characters from left to right, but that is only a checking technique. It is not a manufacturer-defined code key. Read the first characters, the characters around each hyphen, and the ending back to the photograph until the complete string matches exactly.

Preserve the manufacturer's punctuation and do not expand a partial number into a complete one. A note such as "6ES7214...1AG40..." is useful partial evidence when the ending is unreadable, while a completed ending copied from a different record would hide the uncertainty. Mark the missing positions and attach the photograph.

Interpret specifications only after finding an exact manufacturer record for the complete article number. That keeps two separate jobs separate: transcription says what characters are visible, while the product record says which catalog article and specifications those characters identify.

The family name alone can hide a material specification difference. Siemens lists 6ES7214-1AG40-0XB0 as CPU 1214C DC/DC/DC with a 20.4 V to 28.8 V DC supply range, ten 24 V DC digital outputs, and no relay outputs. Those facts come from the exact product data, not from decoding the middle characters.

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The exact product records support the specification contrast. They do not establish mounting equivalence or interchangeability.

Siemens lists 6ES7214-1BG40-0XB0 as CPU 1214C AC/DC/relay with an 85 V to 264 V AC supply range and ten relay outputs. The current records give both articles the same external dimensions of 110 mm by 100 mm by 75 mm, but equal dimensions do not establish the same mounting details, terminal arrangement, project compatibility, or substitution approval.

Do not turn this comparison into a replacement decision. The supply and output specifications are different, so a qualified reviewer must check the installed design, wiring, application, approved successor information, firmware requirements, and site change controls before any substitution. This guide only helps assemble the identity evidence for that review.

When the photograph shows only "CPU 1214C", ask for the complete article number rather than choosing between variants. When it shows a complete article number, link the exact manufacturer record in the request so the reviewer can see which specifications were verified and when.

Keep the article number, each visible version marking, and any software-reported value as separate sourced facts. The current Siemens product data for both exact examples lists firmware version V4.7 and STEP 7 V20 or higher under General information. That is current catalog data, not proof that an installed CPU is running V4.7.

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A catalog firmware listing does not prove the installed firmware state. Each observed or published value keeps its own source.

If a version string is visible in a safe photograph, copy its printed label and value exactly. Do not rename it "hardware generation" unless the manufacturer documentation for that exact marking does so. In particular, this guide no longer describes 0XB0 as a hardware-generation field because the cited Siemens sources do not establish that interpretation.

If an authorized controls specialist supplies an identification value from an approved engineering workflow, record the tool, the value, the device context, the operator, and the observation date. Keep that value beside the photograph instead of silently replacing the printed evidence. A disagreement between sources is a review flag, not permission to choose the convenient value.

Leave a missing version as unknown. The exact article number still supports an exact catalog lookup, but firmware state, project compatibility, and approved replacement status remain separate checks. This separation prevents a current data sheet from being mistaken for a measurement of the installed device.

Record the characters you can read, mark each gap, and keep the original photograph. Do not clean the module, open a cover, move wiring, or remove equipment as part of this guide. If a better view would require cabinet access or contact with equipment, stop and ask authorized site personnel for existing records or a safely planned inspection.

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The flow does not authorize cabinet access, network scanning, device upload, removal, or commissioning work.

Do not connect a laptop, scan the control network, upload a station, or change a device setting solely to complete this identification guide. The Siemens system manual places "Update accessible devices" inside STEP 7 online workflows, and its upload-as-new-station procedure can upload both hardware configuration and software. Network access therefore belongs to an authorized, site-approved controls procedure, not a generic fallback step.

An authorized controls specialist may return identification data from the site's approved workflow. Ask for the complete article number, any reported version, the device context, the tool source, and the observation date. The guide does not prescribe their connection sequence, credentials, interface selection, operating-mode action, or commissioning decision.

When the identity remains uncertain, stop short of ordering or proposing a substitution. Send the partial string, marked gaps, safe photographs, machine context, and source dates for review. A visible uncertainty is useful evidence because it tells the next reviewer exactly what is known and what still needs an authorized check.

• Copy the complete article number exactly; do not decode 0XB0 or fill unreadable characters from another record.
• Use exact Siemens product records to compare specifications, but do not infer mounting equivalence or interchangeability.
• Keep visible markings, catalog values, and authorized tool readings as separate facts with sources and dates.
• Stop before cabinet contact or network access; send partial evidence for an authorized source check.

• PLC and CPU identification hub
• How aliases and abbreviations change a reference
• Audit a control cabinet before removing anything