What the conformal coating buys you in a dirty control room
The 6AG1952-1AL00-4AA0: This is the SIPLUS version of the standard S7-400 RAM card (6ES7952-1AL00-0AA0) with conformal coating applied — IPC-CC-830A Class A, which means the board assembly is sealed against conductive contamination, humidity, and corrosive gas exposure up to EN 60721-3-3 class 3C4 limits. The coating also qualifies the card for environments with salt spray (ISA-71.04 level LC3) and oil mist (level LB3), so it belongs in cement plants, chemical processing, or any panel where airborne grit and condensation eat uncoated electronics.
Temperature range and altitude derating — the real operating envelope
Rated for 0 °C to +60 °C ambient at normal atmospheric pressure (1 140 hPa to 795 hPa, corresponding to -1 000 m to +2 000 m altitude). Above 2 000 m the max ambient drops by 10 K per altitude band — at 5 000 m the ceiling is +40 °C — so if the cabinet sits at elevation, budget the derate into the thermal design.
Memory and system fit for S7-400 racks
2 MB RAM card — the S7-400 CPU uses this as load memory for program blocks and data; the RAM type means the contents are volatile and reloaded from the CPU's memory card or programming device on power-up. Compatible with all S7-400 rack types that accept the standard memory card form factor — the SIPLUS variant is a drop-in replacement for the standard 6ES7952-1AL00-0AA0 in any slot the CPU expects a RAM card.