Sensitive Continuity Checker

  
This continuity checker (built around an LM339 quad comparator with open-collector outputs) eliminates false r
Sensitive Continuity Checker - schematic

eadings because of coils or low-resistance devices in a circuit. Ul is a comparator that acts as a sensing amplifier for the bridge circuit (Rl and Dl, R3 and the unknown resistance, Rx that is connected across the test leads. When iTis less than this predetermined value (by the setting of Rl), the LED lights and B21 sounds.




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