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The three decisions that choose between absolute and incremental rotary encoders, plus resolution, interface and protection levels that finish the spec.

What aircraft, aerospace and aviation connectors actually mean in procurement, which standards govern each, and where industrial circular connectors fit.

Which conductor goes on which pin of a 4-pin aviation connector, how to terminate the shield, and the grounding rules that prevent intermittent faults.

GX16, GX12, LD16 and SD16 mount in the same panel holes but differ in shell, sealing and current. Dimension tables, pin charts and substitution rules.

AC-15 gives a contact 4 A at 240 V; DC-13 gives the same contact 0.3 A at 250 V. The categories, the test duties behind them, and the PLC dry-circuit floor.

A starter is five tested parts, not a big contactor. Worked sizing for a 15 kW pump and a 7.5 kW fan, plus the five mistakes that survive commissioning.

Soot film cleans; carbon tracking never does. Tell the two apart, set the interval by environment, and use insulation resistance trends to pick the real cleaning date.

Ex d means containment, not prevention. Decode the marking, budget the heat, and buy a certified assembly instead of certifying a contactor by accident.

A permanent magnet contactor holds closed for free; an electromagnetic one burns 60-300 kWh a year staying closed. Compare the holding loss, dips and failure modes.

Every number on a contactor nameplate comes from IEC 60947-4-1. Here is the clause-by-clause map - and the test report you should demand.

DC has no zero crossing, so voltage rating, time constant and pole configuration decide everything. A five-step selection for BESS, PV and EV charging.

Three mechanisms keep a contactor closed after power off: welded contacts, remanence and mechanical failure. Each leaves a different fingerprint.