| 摘要 |
Runout of a high speed, small diameter test rod in a drill spindle is measured by locating a pair of magnetic cores on opposite sides of the rod to establish a pair of magnetic circuits which include the air gaps between the rod and each of the cores. Coils on the cores are driven by square waves, which are differentially combined at the junction of the coils. The square waves have a frequency many times greater than the rotational speed of the rod, and amplitude of successive half cycles of the combined square waves are sampled after suitable delay times. The difference between the samples is a measure of the instantaneous rod runout while the rod is rotating. The instantaneous runout signal varies sinusoidally as the rod rotates and is peak detected to display the magnitude of the peak to peak voltage as a measure of rod runout. An auto-centering compensation is provided to prevent the runout signal from saturating because of static offset of the cores from a precisely centered position on opposite sides of the rod. A signal representing the average position of the rod centerline during its rotation relative to the two cores is employed to modulate opposite phase square waves which are combined with the sensor output from the junction of the two coils so as to diminish the sensor output according to the amount of static offset.
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