OPERATION
4-3
Short location example
In the example circuit in Fig 4-1, a short circuit exists between the output of U1 and the
input of U2. Board power is disconnected, and the Needle Probes are placed at A and
E. The resistance of the tracks via the short gives a reading and a tone.
Moving the probe from A to B gives a lower reading and a
higher
tone. This indicates
that the probe has moved
closer
to the short.
Moving the probe from B to C gives a higher reading and a
lower
tone, indicating that
the probe has moved
beyond
the fault.
This implies that the fault is between B and C.
Now move the other probe from E to give the lowest reading and the highest frequency
tone. When the reading is below about 15 m
Ω
, the probes should be within a few
millimetres of the short and the tone changes to a warble.
Fig 4-1 Locating a short circuit
Summary of Contents for Toneohm 550A
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