| 摘要 |
An autobalance control circuit (80) for use in a moisture sensor which senses moisture on the surface of a transparent material. The moisture sensor includes detectors (44, 54) for receiving emitter signals (42) which are influenced by moisture on the transparent material. The moisture sensor further includes a pre-demodulation circuit (60) for attenuating unwanted signal components in the detector output signal while amplifying the useful signal components for further processing by a microcomputer (65). An autobalance circuit (80) is provided for receiving the pre-demodulation circuit signal (64) and providing an autobalance signal (98) 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.
|
