Originally Posted by
HeliComparator
Well just to be picky, not "high voltage pulse" since the "chip" will be making a short circuit, across which it is very difficult to generate a "high voltage". In fact is a measured dose of charge (set current for a set time) such that a small chip will be vapourised, a larger chip won't be.
I presume that the body of the chip detector has a high-ish value resistor across it and the test procedure checks that this resistance is in circuit. Open circuit (wires disconnected) would therefore not give a good test, and of course a short circuit (chip present) would leave the light permanently on. A bit like the fire detection system in reverse!
Some Aircraft like the S76 also use a set of contacts on the Chip Detector relay to latch and hold the Chip light on. Not sure if this aircraft is a latch hold circuit or not.
Fire Detectors use an Integrity Resistor to prevent False Fire Warnings. Chip detectors do NOT have any Integrity resistors.
Test resistors are used on Fire Bottle, Winch Cut, ETC type Squibs to limit the current during integrity test.