Measuring amps

["Rhett T. George" <rtg ee duke edu>]

 - Greetings -

Several different types of non-invasive ammeters (do not have to break
the circuit to use them) have been discussed in the past several days.
An old design not yet mentioned is held against the insulated cable
carrying D-C.  One model for generators, another for starters.  The 
circular magnetic field around the cable interacted with the magnetic
circuit of the meter, causing the needle to rotate against the return
spring.  Simplicity itself, even if it was not very accurate.  In the
'20's and '30's these might have been priced under a dollar.

                                        Rhett George