| 摘要 |
A system for sensing paper on a paper roll includes an ultrasonic transducer positioned to be in contact with an outer surface of the paper roll; a transmitter circuit in communication with the ultrasonic transducer, the transmitter circuit providing a transmit signal to the ultrasonic transducer, the ultrasonic transducer generating an ultrasonic signal in response to the transmit signal; a receiver circuit in communication with the ultrasonic transducer, the receiver circuit providing a received signal indicative of an ultrasonic return echo from the paper roll, the ultrasonic return echo resulting from the ultrasonic signal interacting with the paper roll; and a processor circuit, in communication with the transmitter circuit and the receiver circuit, that determines an amount of paper remaining on the paper roll in response to the transmit signal and the receive signal, the processor providing an output signal when the amount of paper remaining falls below a threshold.
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