Wiring Harnes News Nov-Dec 2021 - Page 25

INDUSTRIAL INFO-TAINMENT Wiring Harness News NOVEMBER / DECEMBER 2021 25

Automated Testing for Harnesses ( Part 2 )

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initially knows only that the failure occurred between the source net and the group of nets held at ground . Therefore , it subsequently executes a search routine to identify the nets that are shorted .
A similar process applies to high voltage testing . However , high voltage testing typically includes two separate tests – Dielectric Withstand ( DW or DWV ) and Insulation Resistance ( IR ). Again , we ’ re looking at this briefly to understand the basic processes , so we ’ ll use simple definitions . A DW test ensures that the device under test withstands a specified voltage for a required period of time . The test equipment is designed to identify transient conditions , like an arc , in which the current spikes rapidly . An IR test ensures that the resistance between circuits meets a required minimum .
A DW test can be performed using AC or DC voltage and the pass / fail threshold is set as a maximum current in microamps or milliamps . DW is a “ pass-if-under ” test meaning that the test passes if the current measurement remains below the threshold for the duration of the test ( lower current flow between isolated nets is better ). An IR test is always performed using DC voltage with the pass / fail threshold set as a resistance , typically megohms or gigaohms . IR is a “ pass-if-over ” test meaning that the test passes if the measurement is greater than the threshold ( greater resistance between isolated nets is
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