| 摘要 |
A probe defining a transmission line for use with a measurement instrument includes a pulse circuit connected to the probe for generating pulses on the transmission line and receiving reflected pulses on the transmission line. The probe comprises a conductive outer sleeve for mounting to a process vessel. A center conductor is coaxial with the outer sleeve for conducting the pulses. A primary seal element between the outer sleeve and the center conductor is spaced a select distance from a near end of the outer sleeve. A secondary seal element between the outer sleeve and the center conductor is spaced proximate the near end of the outer sleeve, to define a generally tubular space between the primary seal element and the secondary seal element. A dielectric insert fills a portion of the tubular space proximate the secondary seal element. A leak detection tube is in the tubular space between the dielectric insert and the primary seal element. The leak detection tube has an inner diameter greater than an outer diameter of the center conductor to define a void. The dielectric insert and the leak detection tube provide a substantially continuous uniform impedance under dry conditions. |
