| 摘要 |
<p>Apparatus for monitoring the composition of a medium comprises an elongated member for insertion into said medium. An array of transmitters and receivers of ultrasonic waves is disposed at intervals along at least part of the length of the member, and reflector means provided to reflect transmitted ultrasonic waves to the receivers. The reflector means is supported by, but laterally spaced from, said member so that the medium occupies the space between said elongated member and the reflector means so that transmitted ultrasonic waves pass through said medium en route to the receivers. Monitoring means are provided to give a signal dependent upon the time taken for an ultrasonic sound wave to travel from a transmitter to a receiver associated therewith.</p> |
