Description

The 6ES5100-8MA11​ is a Siemens SIMATIC S5-100U CPU 100 processor module — the entry-level CPU for the S5-100U rack system, delivering 10 digital inputs (24 V DC), 6 relay outputs (2 A NO), 2 analog inputs (0–10 V / 0–20 mA jumperable), and 1 analog output (0–10 V) integrated directly on the CPU face, plus a proprietary S5-100U backplane that accepts up to 3 SM 100 expansion slices (digital/analog) for I/O counts well beyond the S5-90U ceiling. Powered from 24 V DC and programmed via STEP 5 over the front 15-pin PG interface, the 6ES5100-8MA11​ occupies the “growable compact” slot in the S5 hierarchy: smaller than an S5-115U rack (no EU distribution, no PROFIBUS native), bigger than an S5-90U (which is fixed-I/O, no expansion). It’s the typical choice for packaged equipment, small-machine cells, skid-mounted process units, and retrofit relays-in-a-box where 10–50 I/O is the range and STEP 5 ladder portability upward to S5-115U/155U matters.

Application Scenarios

A municipal-lift-station package OEM builds standardized 4-pump wet-well stations — each station has 4× 7.5 kW submersible pumps, 2× magnetic-levitation level transmitters, 2× inflow-proportional PSA-based DO sensors (for the aeration bypass leg), and a local HMI. Originally they used S5-90U (6ES5090-8MA11) on the 2-pump skids, but the 4-pump version blew past the 10DI/6DO ceiling (needed 12 DI + 10 DO + 4 AI + 2 AO). Instead of jumping to an S5-115U UR rack (which would mean a bigger wall-mount enclosure and a separate PS module + IM), they specced the 6ES5100-8MA11​ on the S5-100U rack: CPU 100 integrated I/O covers the HMI buttons/beacons/alarm-horn + 2 level transmitters + 1 analog outflow-trim AO, and one SM 101 (16 DI) + one SM 122 (8 DO relay) + one SM 104 (4 AI) fill out the pump interlocks, transducer redundancy, and DO-loop trim. Total I/O: 26 DI / 14 DO relay / 6 AI / 2 AO — all on a backplane barely larger than the S5-90U’s footprint. STEP 5 ladder ported 80% from the 2-pump S5-90U version (same instruction set, same addressing style), and the 6ES5100-8MA11‘s PG port talks to the same Siemens PC Adapter the OEM already owns for their S5-115U fleet. Five years and 40 stations later, the OEM still stocks two 6ES5100-8MA11​ spares — “it’s the 90U with growth room, without the 115U’s rack tax.”

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