Thomson Ammeter Collection Nov 23, 2006
Today I learned what an ammeter is. (Thanks Wikipedia!)
In the Rankine station control room, you'll find banks of switches, gauges, meters, etc. corresponding to the alternators in the Power House. This is where the station operators regulate the power and control the operation of the station.
This photo shows—among other things—the ammeters (Ampere Meters) which are used to measure the amount of current. This isn't the only thing measured.
I'm not going to pretend I understand the nuance (or even generalities), so I'll refer you to an excellent page by Professor Mark Csele: