Siemens 6ES7321-1FH00-0AA0 Programmable Logic Controller Module

Siemens 6ES7321-1FH00-0AA0 is a SIMATIC S7-300 SM321 digital input module that provides 16 isolated AC inputs for the backplane, designed for use in SIMATIC S7-300 automation systems. It accepts nominal input voltage of 120/230 V AC (47–63 Hz) and uses galvanic isolation between channels and the backplane via optocouplers, with isolation tested up to 4000 V DC. Each channel reads a logical "1" within 79–264 V and a "0" within 0–40 V, drawing a typical input current of about 6.5 mA at 120 V (60 Hz) or 16 mA at 230 V (50 Hz). The module integrates a 20‑pin front connector and measures 40 mm wide, 125 mm high, and 120 mm deep, weighing about 240 g. It draws power from the backplane at 5 V DC, up to 29 mA, with typical power losses around 4.9 W. As a 16‑channel digital input card, it is suitable for monitoring sensors and control signals in industrial machines, processes, and safety/interlock circuits, and is compatible with the broader SIMATIC S7-300 ecosystem and spare-part catalogs.