CEMB USA C202 - Manual (Page 20)

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5.6 - Eccentricity measurement (EMS optional)
The much enlarged fi gures show the outer tyre surface and axis of wheel rotation.
Fig. A shows measurement of the total Peak-to-Peak eccentricity defi ned as maximum radial deviation of the tyre
surface.
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Fig. B shows measurement of the eccentricity of the 1st
harmonic, i.e. the eccentricity of that circle which “reco-
pies” the tyre shape, by averaging the local deviations
of the tyre from the round shape.
Obviously the P.P. measurement is normally greater
than that of the 1st harmonic. Tyre manufacturers
normally supply two different tolerances for the two
eccentricities.
At the end of the balancing spin it is possible to automatically measure the eccentricity of the tyre through the
SONAR sensor installed on the guard. The sensor should be positioned by hand in front of the tyre tread.
GRAPH 1 : represents the actual Peal-to-Peak eccentricity.
GRAPH 2 : represents the eccentricity of the 1st harmonic. For a wheel to be in optimum conditions, such
graph should approach a straight line.
When the wheel is moved, the cursor on the screen indicates the actual value, with the phase referred to the
eccentricity measurement sensor.
NOTE: Should the wheel stop before having completed the eccentricity measurement, a message appears
on screen instructing you to slowly turn the wheel by hand in order to complete the measurement.
GRAPH 1 - (red)
GRAPH 2 - (yellow)