| 摘要 |
<p>Clamped (12,13) to one of the ribs (11) on the refrigerator condenser (10) is a head (3) containing a transducer which emits infra red radiation and another which is sensitive to reflected infra red. The control unit (4) has a power supply (7) which feeds the emitting transducer, via a transmitter circuit (8) and a unit (9) which receives the sensing transducer output. The receiver output is compared (14) with a fixed reference level (15). The comparator output is amplified (16) and fed to an adjustable timer (17). The timer has three outputs: to a relay (19) and to the 'Freeze' (5) and 'Defrost' (6) indicators. As ice builds up on the black surface of the rib (11), an increasing amount of infra red light is reflected to the sensor until the defrosting mechanism is triggered, via the wiring (21,22,23) from the relay contacts (20).</p> |
