How Ammeters Work

 In the spirit of the great late "one-take" Frank Sinatra, I have the following admission and correction to make to this video, rather than re-doing it.

At one point I misspoke and said that the "one wire from the battery to the horn relay only sensed the flow of current". In fact that wire carries the full load.

I meant to say that the Gauge and its wiring only sensed the flow of current. Probably you were so intent on my acting and/or the gauge's action you missed that anyway. 

 Ammeter (Shunt Meter) Wiring Explained