摘要 |
An inexpensive and accurate device for sensing rotor position and detecting rotational speed over a broad range of speeds in an electric motor includes a sense ring magnet (200) and two analog Hall effect sensors (108, 109, 722). The sense ring (200) is magnetized in an alternating north-south fashion wit h a number of poles that correspond to a number of motor field poles. The Hall effect sensors (722) are placed so that they measure magnetic flux tangentia l to the sense ring. The Hall effect sensors (722) are preferably located at a distance from the sense ring where the Hall effect sensor output waveforms a re substantially triangular, with a highly linear portion centered at zero flux between the minimum and maximum waveform peaks. The linear portions of the waveforms are decoded using an A/D converter and control software to provide an accurate measure of the rotor (724) position.
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