Description
The Siemens 6ES5095-8MA01 is the central unit of the SIMATIC S5-95U compact controller — a rarity in the S5 family because it crams the CPU, power supply, digital I/O, analog I/O, and a firmware PID block into a single DIN-rail housing with no rack, no backplane, no separate PSU module. Designed for single-machine and small-process loops, the 6ES5095-8MA01 was Siemens’ answer to “I need a complete controller in one slice” back when the S5-135U/155U rack monsters were overkill.
Application Scenarios
A textile-finishing OEM in Lancashire still runs a dozen 1994-vintage dye-beck sets, each originally specced around a Siemens 6ES5095-8MA01. The controller handles the beck’s entire loop: 16 DI for door interlocks, level floats, and temperature-limit thermostats; 8 AI pulling 4–20 mA from Pt100 transmitters and conductivity cells; 16 DO driving 24 V DC contactors for circulation pumps and fill/drain valves; and the onboard PID closing the steam-heat loop onto the single AO that drives the steam-control valve positioner. When one of the 95Us finally threw a RAM checksum fault after 28 years, the plant’s instinct was “rip to S7-1200” — until the integrator priced the panel rewire, the new HMI cutover, and the lost production during commissioning. Instead, they sourced a tested 6ES5095-8MA01 reman unit, dropped it in, restored the STEP 5 archive from the dusty PG floppy image, and the beck was back on steam within four hours. The plant manager’s note: “The program still compiles on STEP 5. The valves still move. Why would I spend £8k to ‘upgrade’ a machine that owes me nothing?”
Parameter
| Main Parameters | Value/Description |
|---|---|
| Product Model | 6ES5095-8MA01 |
| Manufacturer | Siemens (SIMATIC S5-95U) |
| Product Category | Compact Central Unit (CPU + PSU + I/O integrated) |
| Digital Inputs | 16 × 24 V DC (sink/source, typ. 4 mA) |
| Digital Outputs | 16 × 24 V DC, 0.5 A/point, electronic short-circuit limit |
| Analog Inputs | 8 channels, 0–10 V / 0–20 mA, 12-bit resolution |
| Analog Output | 1 channel, 0–10 V or 0–20 mA, 10-bit, ~20 µs conv. |
| Alarm Inputs | 4 (hardware interrupt, bypasses scan cycle) |
| Counter Inputs | 2 (hardware): Counter A = 5 kHz, Counter B = 2 kHz |
| Onboard PID | Firmware block, configurable P/I/D + sample time |
| Expansion | Up to 32 × S5-100U modules via dedicated expansion bus |
| Communication | SINEC L2 (PG/OP interface), RS-485 capable |
| Programming | STEP 5 (PG interface, AS511 protocol; no TIA Portal) |
Technical Principles and Innovative Values
Innovation Point 1: True “everything in one housing” for the S5 class. Most S5 CPUs demand a rack, a PS module, and separate SM 321/322/331/332 cards. The 6ES5095-8MA01 deletes all three — CPU, 24 V regulator, 16+16 DI/DO, 8+1 AI/AO, and PID firmware share one 151 × 154 × 159 mm shell. For a standalone machine (packaging head, pump skid, small burner) that’s the difference between a 9-slot rack and a single DIN slice.
Innovation Point 2: 4 alarm DI + 2 hardware counter DI break the scan-cycle ceiling. Normal S5 DI are polled once per OB1 — a pulse shorter than scan time is invisible. The 6ES5095-8MA01‘s 4 alarm inputs fire a hardware interrupt on every edge and jump to a dedicated routine in microseconds, making them the correct landing zone for E-stop, overtemperature trips, and fast fault latches. The 2 counter DI (5 kHz / 2 kHz) accumulate flow-meter pulses or encoder ticks independently of the scan — something no ladder-network contact can replicate.
Innovation Point 3: Firmware PID with no function module. The 8 AI feed straight into the 6ES5095-8MA01‘s onboard PID block; you tune P/I/D gains and sample interval in STEP 5 and write the result to the single AO. For single-loop temperature, flow, or level control, that’s a complete closed loop without an FM 455 or external loop controller — a big deal in the ’90s, and still the reason these units survive in small-process huts today.
Application Cases and Industry Value
Case 1 — Municipal booster pump station (Netherlands). Four parallel 22 kW centrifugal sets, each with duty/standby logic, suction-pressure transducer (4–20 mA), and a 24 V DC contactor for the soft-starter. The original panel builder used a 6ES5095-8MA01 per set: 8 AI took the pressure + panel thermostats, 16 DO ran the contactors + beacon + SCADA dry contacts, PID held suction at 3.2 bar against variable city-main demand. Thirty years later, three of the four 95Us are still original; the fourth was swapped from stock when its backup RAM battery died unnoticed over a Christmas shutdown. Total cost of “modernization” quoted by a systems house: €42 k for four S7-1200 + G120 + rewire. Cost of keeping the 6ES5095-8MA01 fleet alive with tested spares + a PM battery-swap schedule: ≈ €3 k. The municipality chose the latter and redirected the rest to a VFD upgrade on the lead pump.
Case 2 — Chocolate tempering tunnel (Switzerland). The tunnel’s 12-zone jacket-heat loop runs on a 6ES5095-8MA01 with 3 × S5-100U expansion AI cards (to get from 8 AI → 20 AI for zone thermocouples). The onboard PID drives a 0–10 V signal to the zone-mix valve; the 4 alarm DI catch zone-overtemp from independent mechanical stats as hardware interrupts. When the OEM was asked to “S7-ize” the tunnel for Y2K+25 compliance, they quoted it, then quietly recommended staying S5 because the STEP 5 code was 1 800 NETs and the plant had no appetite to re-validate a food-contact line. A spare 6ES5095-8MA01 sits in the site safe with a “last-changed 2019” sticker.
Related Product Combination Solutions
Keeping a 6ES5095-8MA01 rack alive? These S5-100U expansion modules share its bus:
- 6ES5100-8MA02 — S5-100U digital input expansion (to grow beyond the 95U’s 16 DI).
- 6ES5100-8EA01 — S5-100U digital output expansion (24 V DC, relay options available).
- 6ES5100-8MA03 — S5-100U analog input expansion (adds 8 AI to the 95U’s 8).
- 6ES5100-8EA02 — S5-100U analog output expansion (adds AO channels beyond the single onboard).
- 6ES5798-0AA00 — S5 EPROM memory submodule (for archival program backup outside the RAM+battery).
- 6ES5792-0AA00 — S5 backup battery (3.6 V lithium, the one your PM schedule should be swapping every 2 years).
- 6ES5734-1BD20 / PG cable — AS511 (TTY) cable from modern USB → S5 PG port, since the 6ES5095-8MA01 predates Profibus PG and TIA entirely.
