Jasen Betts wrote in a message to Roy J. Tellason:

 JB>> Otoh electronic ammeters can be installed using the batteries
 JB>> earth cable as a shunt...

 RJT> I have a couple of articles sitting here that describe how to
 RJT> build those,  and should probably have a go at it one of these
 RJT> days

 JB> were you once complaining about having too many "304" op-amps?
 JB> they're ideal for that application. (except you only need one
 JB> op-amp) 

Not me.  I don't even recognize that number as applying to any particular part...

---