8 analog inputs, 52 µs conversion — what it means on the line
The Siemens 6ES7331-7HF00-0AB0 SM 331 module gives you 8 analog inputs with a basic conversion time of 52 µs per channel — fast enough to catch 50 Hz ripple on a 4–20 mA loop without aliasing. It accepts voltage ranges from ±1 V up to ±10 V and current ranges from 0–20 mA, 4–20 mA, and ±20 mA, with input resistance of 50 Ω on current loops and 100 kΩ on the ±10 V range. Rated supply is 24 V DC with reverse-polarity protection; the module draws up to 100 mA from the 5 V backplane bus and dissipates 1.5 W typical.
The module measures 40 mm wide, 125 mm high, and 117 mm deep — it occupies one slot in a S7-300 rack and requires a 20-pin front connector (sold separately).