Our industrial computer runs on DC but the site only has 220 VAC. Should we use the supplied adapter or a DIN-rail power supply?

Both work; choose by where the machine sits. External adapter (brick type): fine for desks, clean control rooms and trial machines. The downsides: it is easy to unplug by mistake, barrel plugs loosen under vibration, adapters are usually rated only for office temperatures, and a loose brick in a cabinet is untidy. DIN-rail power supply: suited to cabinets and field installations. Wiring uses screw terminals, it tolerates a wider temperature range, has status LEDs and often a fine output adjustment. Choose one with safety certification and enough spare capacity. Safe wiring: 1. Fit a breaker or fuse on the AC branch feeding the supply. 2. Connect the supply's PE terminal to earth. 3. Use ferrules on stranded wire at the terminals. 4. Choose an output voltage within the machine's input range, usually 12 or 24 VDC; for wide-range machines, 24 VDC reduces current and voltage drop in the wiring. Where mains power is unstable, consider adding a DC UPS after the supply.