| 摘要 |
A system for point-level detection of material within a vessel includes a transmission line probe adapted to be mounted to a wall of the vessel so as to extend within the vessel for contact with material when the material reaches a preselected level within the vessel. Electronics are operatively coupled to one end of the probe for launching microwave energy along the probe. The electronics are responsive to a change in microwave energy reflected from the free end of the probe within the vessel when the material is in contact with the probe, employing time-domain reflectometry techniques, for indicating that the material is in contact with the probe. This change in reflected microwave energy may comprise a change in phase or, more preferably, a change in apparent length of the probe resulting from contact with material having a higher dielectric constant than that of air when air surrounds the probe. The electronics preferably are also responsive to a decrease in apparent length of the probe for indicating a failure condition at the transmission line probe or electronics. |
