Patent ID: 7890271
Filing Date: 2011-02-15
Classification: G01P

Abstract:
1. A revolution indicator, comprising: a detecting portion which detects data related to a physical phenomenon resulting from the revolving movement of a measuring object; a fast Fourier transformation computation portion which performs a fast Fourier transform of the data detected by the detecting portion under a first data length to compute first analytical data, and outputs the first analytical data; and a revolution computing portion which computes the number of revolutions of the measuring object; and a variation determination portion which is equipped to make the fast Fourier transformation computation portion compute a plurality of the first analytical data continuously based on the data successively detected by the detecting portion under the first data length and to determine whether there is variation or not among the plurality of the first analytical data computed continuously, wherein when there is the variation among the plurality of the first analytical data computed continuously, the variation determination portion makes the fast Fourier transformation computation portion sequentially output the plurality of the first analytical data to the revolution computing portion, and when there is no variation among the plurality of the first analytical data computed continuously, the variation determination portion makes the fast Fourier transformation computation portion compute second analytical data under a second data length which is longer than the first data length, and output the second analytical data to the revolution computing portion, and the revolution computing portion computes the number of revolutions of the object based on one of the plurality of first analytical data, and the second analytical data.