Transducers
AssigneeSpill-Fire Alarm Systems Ltd.
InventorRaymond W. Norfolk
Life of this patent
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Abstract
A transducer has a chamber containing a substance having a monitorable physical and/or chemical property, for example electrical conductivity, which property changes in correspondence with a change in an external influence, for example, temperature. In one embodiment, the chamber is of elongate form and changes in said monitorable property in any part of the substance along the length of the chamber are monitored by a detection means. In a further embodiment the substance is arranged to undergo an abrupt change in the said property thereof, for example, due to a phase change in the said substance, in response to a predetermined change in the external influence, and detection means is provided to detect such abrupt change.
Claims10
A temperature monitoring device comprising an elongate chamber in the form of a length of tubing containing a solution which undergoes an abrupt change in a physical property thereof due to crystallisation of a substance out of said solution saturated with said substance in response to a predetermined change in the temperature of all or a portion of said solution, and monitoring means for monitoring said property and sensitive to said abrupt change therein.
A temperature monitoring device comprising an elongate chamber in the form of a length of flexible tubing, containing electrodes at opposite ends thereof and an electrically conductive medium extending between said electrodes, said medium comprising a saturated solution of an electrolyte the electrical conductivity of which undergoes an abrupt fall due to crystallisation of said electrolyte out of the solution in response to a predetermined fall in the temperature thereof, and an electrical detection means including an a.c. bridge circuit for monitoring the conductivity between said electrodes so as to produce an electrical output in response to detection of a conductivity change due to occurrence of said predetermined change in the temperature of said medium at any position along the length of the chamber.
A temperature monitoring device of the type comprising an elongated, hollow tube having opposite sealed ends defining a chamber therebetween;
- a pair of electrodes, each at an opposite end of said tube within said chamber, said electrodes forming part of an electrical monitoring circuit and a medium filling said chamber which changes its electric conductivity in response to a change in temperature, characterized by:
- said electrodes having non-corrosive tips of platinum;
- said tube being formed of flexible black, thin walled, plastic tubing of small bore;
- and said medium being an aqueous ionic salt solution saturated with potassium nitrate, normally in liquid state, at -20.degree. C., but subject to abrupt, sudden crystallisation of salts out of said solution in response to a reduction of temperature to thereby trigger said monitoring circuit.
Dependencies are inferred from the claim text.