Moisture sensor with autobalance control
First Claim
1. A method of detecting moisture on the surface of a material comprising:
- providing a sensor mounted to the material and having an emitter for generating an emitter signal which is influenced by the presence of moisture on the surface of the material, and a detector for receiving the emitter signal and contributing to the production of a detector output signal;
filtering unwanted signal components from the detector output signal;
amplifying the detector output signal to produce an amplified signal; and
at least partially canceling the detector output signal thereby reducing clipping of the amplified signal.
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Abstract
An autobalance control circuit for use in a moisture sensor which senses moisture on the surface of a transparent material. The moisture sensor includes detectors for receiving emitter signals which are influenced by moisture on the transparent material. The moisture sensor further includes a pre-demodulation circuit for attenuating unwanted signal components in the detector output signal while amplifying the useful signal components for further processing by a microprocessor. An autobalance circuit is provided for receiving the pre-demodulation circuit signal and providing an autobalance signal to the pre-demodulation circuit input. The autobalance signal at least partially cancels the detector output signal to prevent saturation of the pre-demodulation amplifier when undesirable detector output signal amplitudes are encountered. By preventing saturation of the moisture sensor circuitry, the autobalance circuit allows the sensor to continue to operate in the presence of large drops of moisture while having sufficient gain for detecting small droplets of moisture.
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Citations
20 Claims
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1. A method of detecting moisture on the surface of a material comprising:
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providing a sensor mounted to the material and having an emitter for generating an emitter signal which is influenced by the presence of moisture on the surface of the material, and a detector for receiving the emitter signal and contributing to the production of a detector output signal;
filtering unwanted signal components from the detector output signal;
amplifying the detector output signal to produce an amplified signal; and
at least partially canceling the detector output signal thereby reducing clipping of the amplified signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of detecting moisture on the surface of a material comprising:
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providing a sensor mounted to the material and having an emitter for generating an emitter signal which is influenced by the presence of moisture on the surface of a material, and a detector for receiving the emitter signal and contributing to the production of a detector output signal;
filtering and amplifying the detector output signal to produce a pre-demodulation signal;
averaging the pre-demodulation signal to produce an autobalance signal;
combining the autobalance signal with the detector output signal to at least partially cancel the detector output signal to prevent saturation of the pre-demodulation signal. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A method of detecting moisture on the surface of a material comprising:
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providing a sensor mounted to the material and having an emitter for generating an emitter signal which is influenced by the presence of moisture on the surface of the material, and a detector for receiving the emitter signal and contributing to the production of a detector output signal;
filtering unwanted signal components from the detector output signal;
amplifying the detector output signal to produce an amplified signal;
generating an autobalance signal providing a delayed representation of the detector output signal; and
combining the autobalance signal with the detector output signal to at least partially cancel the detector output signal thereby reducing clipping of the amplified signal. - View Dependent Claims (16, 17)
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18. A method of detecting moisture on the surface of a material comprising:
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providing a sensor for producing an output signal which is influence by the presence of moisture on the surface of the material;
filtering unwanted signal components from the output signal;
amplifying the output signal to produce an amplified signal;
generating an autobalance signal providing a delayed representation of the output signal; and
combining the autobalance signal with the output signal to at least partially cancel the output signal thereby reducing clipping of the amplified signal. - View Dependent Claims (19, 20)
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Specification