The ornamental design for an instrument for detecting which electrical plug is connected to a particular circuitbreaker, as shown.
FIG. 1 is a top, side and rear perspective view of an instrument for detecting which electrical plug is connected to a particular circuit breaker, showing my design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a side elevational view thereof, the side opposite that shown in FIG. 3 being the mirror image thereof; and,