Electronic edge finder: how do they work?

[tumutbound]

The tip is insulated and when it touches the workpiece, the circuit is completed and the LED lights.
Too bad if you're machining plastic.

[irving2008]

The tip is insulated and when it touches the workpiece, the circuit is completed and the LED lights.
Too bad if you're machining plastic.

that means the circuit is tip, workpiece, table, column, head, chuck... surely not... a tad tenuous at best...

[John S]

that means the circuit is tip, workpiece, table, column, head, chuck... surely not... a tad tenuous at best...

Only as tenious as power station, sub station, machine tool and neutral,
is 36,000 miles a second or whatever good enough ?

[irving2008]

Only as tenious as power station, sub station, machine tool and neutral,
is 36,000 miles a second or whatever good enough ?

not speed John, connectivity... surely relying on all those having a good or any electrical connection to each other is tenuous?