| 摘要 |
<p>A level sensor (112) emits a signal from a sonic emitter (114). When the signal reaches the end of an outwardly diverging metal cone 130 it disturbs the air located over the end of a dividing wall (132) of the cone, and a receiver (116) recognises that disturbance. The time taken between the signal being omitted and received over the fixed distance is used to give an indication of the speed of sound in the environment. The emitter (114) then emits a further signal which is reflected back off the surface of a liquid to the receiver (116), and the time taken for that further signal to be emitted and received is adjusted in accordance with the time taken for the previous signal to travel the fixed distance in order to give an accurate indication of the liquid level.</p> |
