02/25/00
Microsense II Model 5300 Gaging System - 25
Setup Suggestions: Runout Measurements
Runout measurements examine variations in moving or rotating objects. In measurements where a large
runout is expected (close to the full range of the gage), it is important to make certain that the probe is
actually in range over the entire surface to be measured before attempting dynamic measurements. This
ensures that an overrange condition will not occur even though the runout (change in displacement) does
not exceed the range of the gage. In this case, instead of positioning the probe for a zero readout over any
point on the surface, it may be more convenient to position the probe for an approximate full scale indication
at a known low point on the surface (such as the lobe of the cam or major diameter of an eclipse) or to
position for an approximate negative full scale reading at a known high point on the surface.
If the change in runout is measured with respect to the change in rotational speed or start up "chatter" of a
spindle, the fullest dynamic range of the probe can be obtained by making a single rotation and/or a single
longitudinal pass along the section to be measured. While doing this, observe the displacement output of
the probe and reposition the probe to balance the positive and negative meter deflections over the surface
to be measured. If the largest positive reading is greater than the largest negative reading, the probe is too
far and should be moved closer. If the largest negative reading is greater than the largest positive reading,
the probe is too close and should be farther away.
The figure shown below illustrates the effects of the datum reference determined by probe position on
runout measurements. When the probe is too far from the examined surface (a), an overrange condition
may result for negative peaks. Similarly, when the probe is too close to the examined surface (b), an
overrange condition may result for positive peaks. The probe should be placed so that the nominal reading
is halfway between the two peaks (c), to allow all measured points on the moving surface to be in range.
Selecting a good datum reference allows "exaggerated" peaks due to axis movement, vibration, or startup
chatter to also remain in range (d).
O/R
Meter
Range
Meter
Range
O/R
Meter
Range
Meter
Range
(a)
(b)
(c)
(d)
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
