Patent ID: 8526013
Filing Date: 2013-09-03
Classification: G01B,G01D

Abstract:
1. A batteryless absolute encoder for detecting an absolute position of a spindle to be detected, the batteryless absolute encoder comprising: a plurality of rotary absolute position detectors each having a rotary shaft and coupled to each other via a gear mechanism; an absolute position computing section for computing the absolute position of the spindle, including the number of revolutions of the spindle, on the basis of a plurality of detection signals output from the plurality of rotary absolute position detectors; an absolute position storing section provided with a non-volatile memory for storing an absolute position output from the absolute position computing section when electric power is turned off; and a determining section for comparing the absolute position output from the absolute position computing section when the electric power is turned on and the absolute position stored in the non-volatile memory and outputting an alarm signal if a difference between the two absolute positions is larger than a predetermined value, wherein: the absolute position storing section includes a counter section for storing the number of times that an upper limit for a detection range of the absolute position is exceeded, the upper limit being defined based on a combination of respective numbers of teeth of gears included in the gear mechanism, and the absolute position computing section computes a current absolute position of the spindle on the basis of the number of times that the upper limit for the detection range of the absolute position is exceeded, which is stored in the counter section, and the absolute position computed on the basis of the plurality of detection signals.