CEMB USA N300 - Manual (Page 38)

6 - 4 Balancing function
plane to which the sensor must be applied, which must always remain connected to
channel A of the N300 instrument. The correction displayed relates to the same plane on
which the detector is applied.
Warning: Two-plane balancing with a single sensor involves moving the same
detector from one plane to another various times, but it must always be
repositioned in the exact same position each time. For this reason the use of
threaded holes is strongly recommended as they minimise unavoidable errors
introduced by moving the sensor. However, the procedure is long and arduous and
therefore not recommended for those who need to use it frequently: the use of two
sensors is recommended in such cases.
Unbalance measurement and the simultaneous calculation of the correction mass can be
started and stopped by pressing . Field balancing a rotating body is more often than
not an iterative procedure:
- a measurement is taken to determine the correction mass required
- the required mass is added to the rotating body, trying to observe the value and
position as much as possible
- a new unbalance measurement is taken to verify the effects of the correction
performed
-
if the residual unbalance is still too high, it must be corrected again, and so on
When the correction required is lower than the desired tolerance, the balancing process can
be considered complete. However, at this point it is advisable to verify the residual
vibration, both of the synchronous component 1xRPM (connected to the unbalance), and
the Overall global value (generated by other causes). The vibrometer function must be used
for this purpose (see Chapter 5 – Vibrometer function) setting the same value for the
synchronous filter width.
Note:
If the signal is unstable the measurement value can oscillate considerably; in such
conditions it is best to reduce the synchronous filter width for greater accuracy (see
5 – 4 Synchronous filter width) and consequently repeat the calibration.
Warning:
To ensure reliable results, the velocity of the rotating body should be as close as
possible to that of the various calibration steps when the measurement is taken. As
a general indication, variations of about 5%, more or less, can be considered
acceptable.
To remind the operator that calibration is required after any of the balancing parameters
are changed, they can only be changed from the calibration page (see 6 – 6 Calibration
procedures), and not directly from the unbalance measurement page.