What this FX3U-48MT/ES-A is
I've had a hundred of these on the bench – the Mitsubishi FX3U-48MT/ES-A is a 48-point main unit with 24 transistor sink outputs in a compact package. It's the workhorse of the FX3U line for mid-size machines where you need fast, reliable sinking outputs for valve banks, drives, or indicator banks. Power draw is 40 W, which means it won't cook the enclosure even in a tightly packed panel. It runs on a universal 100-240 VAC supply – no separate 24 VDC supply needed for the CPU, just the field I/O power.
The FX3S-30MT/ES is smaller – 30 I/O total – but the FX3U-48MT/ES-A packs nearly 60% more I/O points. If your panel was laid out around the FX3S-30, this unit won't drop in without rewiring the terminal block and updating the I/O map. The FX3U also has more counters (235 vs 32 general-purpose on the FX3S) and timers (512 vs a smaller pool). For a line item that needs the extra capacity, the FX3U is the right choice; for a simple 30-point job, the FX3S is lighter on the budget.
What to know for panel wiring and commissioning
Transistor outputs are sink type – switch the low side. The output points deliver 0.5 A per point, 0.8 A total per common. For high-speed outputs Y000 and Y001, response is 5 µs on/off; the rest are 0.2 ms. Input response is about 10 ms unless you use the digital filter on X000–X017 to drop it as low as 10 µs for position detection.