Proximity sensor combining impedance, frequency and decay constant information
First Claim
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1. A system that compensates for temperature drift in a sensing coil in an extended range inductive proximity sensor, comprising:
- a measuring component that measures voltages in a resonant damping circuit in the proximity sensor before and during a damped oscillatory voltage phase; and
a control component that analyzes information associated with the measured voltages to derive a gamma value related to a time constant of the resonant damping circuit and isolates a portion of inductance caused by a target to determine whether the target has been sensed.
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Abstract
Systems and methods are disclosed that compensate for temperature drift in a proximity sensor, such as an extended range inductive proximity sensor. Voltage measurement can be taken before, and during damped oscillatory decay of a voltage in a resonant circuit in the proximity sensor to determine a value, γ, associated with an inductive time constant for the resonant circuit. A target-induced inductance value can be isolated, via manipulation of the gamma value, and compared to a predetermined threshold value to determine whether the target has been sensed by the proximity sensor.
26 Citations
22 Claims
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1. A system that compensates for temperature drift in a sensing coil in an extended range inductive proximity sensor, comprising:
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a measuring component that measures voltages in a resonant damping circuit in the proximity sensor before and during a damped oscillatory voltage phase; and a control component that analyzes information associated with the measured voltages to derive a gamma value related to a time constant of the resonant damping circuit and isolates a portion of inductance caused by a target to determine whether the target has been sensed. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for compensating for temperature drift in a proximity sensor, comprising:
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determining an RC time constant for a resonant circuit in the proximity sensor; pulsing a current for a period of approximately one RC time constant through the resonant circuit to charge a capacitor therein and to mitigate current consumption by the proximity sensor; determining a first voltage across the resonant circuit; causing the voltage across the resonant circuit to decay for a predetermined time period; and determining a second voltage across the resonant circuit after the predetermined time period. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A system that compensates for temperature drift effects on a sensing coil in an extended range proximity sensor, comprising:
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means for determining a time constant value for a resonant damping circuit in the proximity sensor; means for determining a portion of total circuit inductance due to a target; and means for comparing the value of the target-induced inductance value to a predetermined threshold value. - View Dependent Claims (22)
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Specification