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Maxim > Design Support > Technical Documents > Application Notes > Amplifier and Comparator Circuits > APP 4234
Keywords: continuity, ac continuity, capacitive coupling, go/no-go, cable repair, comparator
APPLICATION NOTE 4234
AC-Based Continuity Tester Finds Single-Ended
Faults
By: Kevin Bilke, Applications Engineer
May 29, 2008
Abstract: This article presents an AC-based continuity tester designed for frontline test and repair jobs.
The circuit provides a simple GO/NO-GO test for localizing faults in multicore cables, allowing one to
open and repair the correct cable end while avoiding the risk of damaging a good connector by opening
it up.
A similar version of this article was featured in Maxim's Engineering Journal, vol. 63 (PDF, 1.3MB).
Overview
This article details an AC-based continuity tester designed for frontline test and repair jobs. The circuit
provides a simple GO/NO-GO test for localizing faults in multicore cables.
Open circuits are more likely at connector ends. By identifying the faulty end, the AC continuity tester
allows you to open and repair the correct cable end and avoids the risk of damaging a good connector
by opening it up. This approach is also useful for testing an installed cable with ends at different
locations.
Circuit Description
Figure 1 illustrates a circuit for a continuity tester that injects an AC signal on one cable wire and then
looks for the absence of capacitive coupling on the other wires. One end of a bad cable typically shows
good AC continuity, while the other end typically has one or more connector pins with no AC continuity.
Because a short in the cable appears as a good connection, the operator can easily confirm that the
tester is operating correctly by simply shorting its test leads together.
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