| 摘要 |
Apparatus for indicating the oil level in a central heating oil tank comprises a battery powered monitoring unit ( 1 ) for mounting on the oil tank which determines the oil level by an ultrasonic signal transmitter/receiver ( 18 ). A first microprocessor ( 14 ) in the monitoring unit ( 1 ) determines the oil level from the ultrasonic transmitter/receiver ( 18 ) and operates a primary transmitter ( 12 ) for transmitting a radio signal which includes data indicative of the oil level. A remotely mounted mains electricity powered receiving unit ( 3 ) comprises a primary radio receiver ( 15 ) for receiving the transmitted signal, and a second microprocessor ( 16 ) in the receiving unit ( 3 ) controls the operation of a visual display unit ( 10 ) for graphically displaying the oil level. The monitoring unit ( 1 ) and the receiving unit ( 3 ) are operable in a teaching mode initially on power-up of the receiving unit ( 3 ) during which the monitoring unit ( 1 ) teaches the receiving unit ( 3 ) its address. The first microprocessor ( 14 ) controls the ultrasonic transmitter for transmitting ultrasonic signals for two predetermined time periods in order to facilitate detection of the oil level as the oil level varies from full to empty.
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