The present invention discloses an abnormal state detecting apparatus in a torque sensor which uses a pair of coils to detect a torque on the basis of a change in inductance.

A sensor for monitoring the interior of a sodium-cooled fast breeder reactor comprises a pair of symmetrical magnetic cores, a magnetostrictive or piezoelectric vibrator element bonded to one of the cores, a primary coil and a plurality of secondary coils surrounding the magnetic cores, and a container enclosing the above members. The primary coil applied with an exciting alternating current generates an acoustic signal voltage indicative of sound, if any, originated in the interior of the reactor. The magnetic flux produced by the exciting current is influenced by the temperature and flow velocity of sodium flowing around the sensor, and corresponding voltage signals resulting from the changed magnetic flux are induced in the secondary coils.

Moisture sensing apparatus that uses slow wave transmission lines. Such transmission lines include a helically wound inner core, a surrounding outer conductor, and a moisture bearing material between the inner core and the outer conductor. Preferably, the transmission line includes a moisture barrier that separates the transmission line into a sealed dry section and a wet section which is in moisture communication with its environment. The moisture sensing apparatus further includes a source of electrical signals on the transmission line, and a moisture sensing circuit, operatively connected to the slow wave transmission line, which senses the moisture content of the moisture bearing material from the velocity of the impressed electrical signals on the slow wave transmission line. Preferably, the velocity of the impressed electrical signals is obtained indirectly using a sing-around measurement technique.

A hydrocarbon detection system is provided for use in a subsea hydrocarbon production installation which includes production tree assemblies, an electro-hydraulic control module located on the sea floor and remote from the production trees, cable assemblies interconnecting the control module with the production trees through magnetic coupling devices. A pair of inductive elements are electrically coupled by the surrounding sea water. Displacement of the conductive sea water by escaping hydrocarbons affects the coupling between the inductive elements to produce a hydrocarbon-presence-responsive output signal. The inductive elements are resonated within a selected frequency range by capacitors coupled with a primary inductor coil by auxiliary windings on a common core element. An excitation signal sweeps over the selected frequency range at a rate effective to produce a peak detected signal at the resonant frequency. The peak output signal is then monitored to form a control signal functionally related to the presence or absence of hydrocarbons in the sea water.

An apparatus for measuring the flow rate of electrically conductive liquids includes two coils disposed in succession as seen in the flow direction of a liquid. The coils are switched in alternation as a primary and a secondary coil. One of the coils is excited with an alternating current as the primary coil, and voltage induced by the excitation in the other of the coils as the secondary coil is measured.