Amplification circuit for increasing variable reluctance sensor output
First Claim
1. An apparatus that measures a characteristic of a machine, comprising:
- a variable reluctance sensor (VRS) coupled to said machine and operative to generate a basic output signal having a basic frequency representative of said characteristic;
a resistive element electrically coupled to said VRS and operative to filter a portion of said basic output signal having a frequency at a prescribed level, said resistive element in combination with an inductance of said VRS generating a filtered output signal, wherein said filtered output signal is indicative of a current produced by said basic output signal; and
a controller coupled to said VRS and operative to determine said characteristic and decouple said resistive element when said characteristic exceeds a prescribed threshold level.
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Abstract
An apparatus and method for measuring a characteristic, such as speed, of a machine. A variable reluctance sensor (VRS) is coupled to a resistive element, which filters a portion of a basic output signal generated by the VRS having a frequency above a prescribed threshold level, thus removing high-frequency noise from the basic output signal. An amplifier amplifies the filtered output signal. The filtered, amplified output signal has an increased signal-to-noise ratio such that the machine characteristic, i.e. speed, can be more accurately measured during a slow speed operation. A controller generates a control signal received by a switching device to decouple the resistive element when machine speed exceeds a prescribed threshold level. Then, the basic output signal is used to measure the characteristic of the machine during normal machine operation.
19 Citations
27 Claims
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1. An apparatus that measures a characteristic of a machine, comprising:
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a variable reluctance sensor (VRS) coupled to said machine and operative to generate a basic output signal having a basic frequency representative of said characteristic;
a resistive element electrically coupled to said VRS and operative to filter a portion of said basic output signal having a frequency at a prescribed level, said resistive element in combination with an inductance of said VRS generating a filtered output signal, wherein said filtered output signal is indicative of a current produced by said basic output signal; and
a controller coupled to said VRS and operative to determine said characteristic and decouple said resistive element when said characteristic exceeds a prescribed threshold level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of measuring a characteristic of a machine having a variable reluctance sensor (VRS), comprising:
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generating a basic output signal from said VRS electrically coupled to a resistive element, said signal having a basic frequency representative of said characteristic;
filtering said basic output signal to remove a portion of said basic output signal having a frequency at a prescribed level, said resistive element in combination with an inductance of said VHS to generate a filtered output signal; and
decoupling said resistive element when said characteristic exceeds a prescribed threshold level;
wherein said filtered output signal represents a current produced by said basic output signal. - View Dependent Claims (12, 13, 14, 15)
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16. A machine system, comprising:
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a machine having a camshaft with a speed wheel mounted thereon, said speed wheel including at least one gear tooth; and
a sensing system electrically coupled to said machine, said sensing system comprising;
a variable reluctance sensor (VRS) adapted to detect a position of said gear tooth and to generate a basic output signal having a frequency representative of said positions;
a resistive element electrically coupled to said VRS and operative to filter electrical noise having a prescribed frequency level from said basic output signal, to generate a filtered output signal;
an amplifier coupled to said resistive element and adapted to boost an amplitude of said filtered output signal and generate an amplified, filtered output signal;
a controller operative to measure a speed-related parameter of said machine and generate a control signal when said speed exceeds a prescribed threshold level; and
a switching device operative to receive said control signal and to move between at least a first position and a second position based on said control signal, wherein in said first position said resistive element is decoupled, and wherein in said second position said resistive element is engaged. - View Dependent Claims (17)
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18. An apparatus that measures a characteristic of a machine, comprising:
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a variable reluctance sensor (VRS) coupled to said machine and operative to generate a basic output signal having a basic frequency representative of said characteristic; and
a resistive element electrically coupled to said VRS and operative to filter a portion of said basic output signal having a frequency at a prescribed level, said resistive element generating a filtered output signal;
a controller coupled to said VRS and operative to measure a speed-related parameter of said machine and generate a control signal when said speed-related parameter exceeds a prescribed threshold level; and
a switching device operative to receive said control signal and to move between at least a first position and a second position based on said control signal, wherein in said first position said resistive element is decoupled, and wherein in said second position said resistive element is engaged. - View Dependent Claims (19, 20, 21)
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22. A method of measuring a characteristic of a machine having a variable reluctance sensor (VRS), comprising:
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generating a basic output signal from said VRS, said signal having a basic frequency representative of said characteristic;
filtering said basic output signal to remove a portion of said basic output signal having a frequency at a prescribed level and to generate a filtered output signal, wherein said filtered output signal represents a current of said basic output signal determining said prescribed level based on an inductance of said VRS and a resistive element; and
outputting one of;
(a) said amplified, filtered output signal whenever a speed of said machine does not exceed a prescribed threshold level, and (b) said basic output signal whenever said speed exceeds said prescribed threshold level. - View Dependent Claims (23, 24, 25)
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26. An apparatus that measures a characteristic of a machine, comprising:
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a variable reluctance sensor (VRS) coupled to said machine and operative to generate a basic output signal having a basic frequency representative of said characteristic, said variable reluctance sensor having an inductance; and
a resistive element electrically coupled to said VRS and operative with said inductance to filter a portion of said basic output signal having a frequency at a prescribed level, said resistive element generating a filtered output signal and a controller coupled to said VRS and operative to determine said characteristic and decouple said resistive element when said characteristic exceeds a prescribed threshold level. - View Dependent Claims (27)
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Specification