The Figure above shows the scope patterns of two windings. The pattern on the left shows the
oscillating frequency of a good coil. The pattern in the middle shows the oscillating frequency of a
coil with a shorted turn. They look very similar until they are superimposed on top of each other.
Note that the coil with the shorted turn has a higher oscillating frequency. This test is only effective
for detecting problems in the first few turns of a coil, which is typically where damage will occur
due to surges and switching transients.