| 摘要 |
A method includes transmitting a measurement-cycle ultrasonic signal from a signal transmitter toward a monitored space. Signals are received at a signal receiver. The signals include a sequence of measurement-cycle echo signals based on the transmitted measurement-cycle ultrasonic signal. Each measurement-cycle echo signal has associated signal strength. The method includes integrating data corresponding to the associated signal strengths for at least a portion of the sequence of measurement-cycle echo signals over time to produce an integrated measurement-cycle echo signal value. The method also includes comparing the integrated measurement-cycle echo signal value to an integrated calibration-cycle echo signal value that corresponds to the monitored space being empty. |
