Magnetic speed sensor with an adaptive threshold circuit for use with a bearing assembly
AssigneeThe Torrington Company
InventorA. J. Santos
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Abstract
A magnetic sensor bearing utilizes an adaptive threshold circuit for signal processing in order to compensate for external factors such as temperature, stress, aging, and external magnetic fields which all affect a fixed reference signal used with a comparator. As the magnetic sensor's output signal drifts due to these external factors, the adaptive threshold circuit causes the reference signals to drift in a complementary manner so that the magnetic sensor bearing continues to function properly in spite of the external factors.
Claims11
A speed sensor assembly for use with a bearing assembly and a rotatable shaft, said sensor assembly comprising in combination:
- means for providing a magnetic signal corresponding to the rotational speed of said rotatable shaft, said means connected to said shaft;
- a solid-state magnetic sensor for detecting said magnetic signal, said sensor providing an analog output signal to a sensor output terminal, said output signal being proportionate to said magnetic signal and the speed of rotation of said shaft;
- means for mounting said sensor on said bearing assembly;
- and
- an adaptive threshold circuit connected to said sensor output terminal, and processing said sensor signal to provide a square-wave digital output signal, said adaptive threshold circuit consisting of:
- a comparator having first and second analog input signal terminals and one digital output signal terminal;
- a first analog comparator input signal terminal connected to said sensor output terminal and having a positive feedback signal from said comparator output terminal connected to said fist comparator input terminal to provide hysteresis;
- and
- a second analog comparator input signal terminal connected to said sensor output terminal and a low-pass filter in series, said low-pass filter consisting of a resistor and a capacitor;
- said comparator being responsive to the relative amplitudes of said fist and second input signals so as to provide a corresponding signal output signal to said comparator output terminal, and
- said adaptive threshold circuit being integrated entirely onto an integrated circuit chip, with the exception of said capacitor in said low-pass filter.
A bearing assembly for use with a rotatable shaft, said assembly comprising in combination:
- a bearing mounted on said shaft, said bearing having a first member connected to said shaft so as to rotate with said shaft, and a second member relatively rotatable relative to said first member and said shaft;
- means for providing a magnetic signal corresponding to the rotational speed of said shaft, said means connected to said shaft;
- a Hall sensor for detecting said magnetic signal, said Hall sensor providing an analog output signal to a sensor output terminal, said output signal corresponding to said magnetic signal and the rotational speed of said shaft;
- means for fixing said Hall sensor to said bearing second member;
- and
- an adaptive threshold circuit connected to said sensor output terminal, and processing said sensor output signal to provide a square-wave digital output signal, said adaptive threshold circuit consisting of:
- (1) a comparator having first and second analog input connected to said sensor output terminal and having a positive feedback signal from said comparator output terminal connected to said first comparator input terminal to provide hysteresis;
- and
- (2) a second analog comparator input signal terminal connected to said sensor output terminal and a low-pass filter in series, said low-pass filter consisting of a resistor and a capacitor;
- said comparator being responsive to the relative amplitudes of said first and second input signals so as to provide a corresponding digital output signal to said comparator output terminal, and
- said adaptive threshold circuit being integrated entirely onto an integrated circuit ;chip, with the exception of said capacitor in said low-pass filter.
Dependencies are inferred from the claim text.