Simple Component and Continuity Tester
This simple project may be used for testing components, as well as checking circuit board tracks, wires and connections for continuity. a small current is passed through the item being tested
and the LED will light brightly, dimly or not at all according to the resistance of the item.

indication:LED bright means the resistance is low, less than about 1kW
-LED dim:-resistance is medium, a few kW
-LED off:-resistance is high above 10k

Parts Required:
resistor: 390W,red LED 5mm diameter, crocodile clips,battery snaps, dot PCB 5 rows × 7 holes

solder bridging can occur between adjacent tracks tracks broken with a track
There cab be almost invisible thread of copper
conducting across the break.In the case of PCB, tracks may be very thin in places or there may be traces of copper bridging between adjacent tracks.

The different testing modes for different components and also more details are given in this pdf:
http://kpsec.freeukdocs/simplet.pdf