Key Features That Matter for Fit
The SR3B261FUSP002: Built-in real-time clock with 10-year backup at 25 °C, drift of 6 s/month at 25 °C (12 min/year over 0…55 °C). That means it holds time through power loss and is usable for time-controlled sequences without an external RTC module. Checks program memory on each power up — no silent corruption when the line bounces. If the program is bad, it won't run, which beats a mystery fault later. 16 discrete inputs, 100…240 V AC. Supply voltage 85…264 V AC. Input current 0.6 mA. Relay outputs: mechanical durability 10 million cycles. Maximum switching rate 0.1 Hz at rated current, 10 Hz unloaded. That's fine for valve or contactor coils; don't plan on fast pulse trains.
Where It Fits – And Where It Doesn't
This is the 16-input, relay-output workhorse for standalone or networked small machines. The cycle time runs 6…90 ms — ladder runs faster than FBD. Good for bin-fill, pump sequencing, or lighting schedules. Not a motion controller; you want a PLC for servo loops.