Method and apparatus for sensing and measuring plural physical properties, including temperature

A method for sensing a property of a fluid in a conduit having an axis, said method comprising the steps of:

• (a) electrically and thermally coupling to said conduit a body of positive-temperature-coefficient material having a plurality of zones deployed in a direction substantially parallel to said axis of said conduit,
• (b) connecting a first one of said plurality of zones through first resistive means to a first level of established electric potential,
• (c) connecting a second one of said plurality of zones through second resistive means to a second level of established electric potential,
• (d) electrically energizing said conduit to cause a first current to flow through said first one of said plurality of zones and a second current to flow through said second one of said plurality of zones while maintaining the material of each of said zones on the steeply-sloping portion of the characteristic curve of its resistance as a function of its temperature, thereby producing first and second voltage drops across said first and said second resistive means respectively,
• (e) thermally exposing said first one and said second one of said plurality of zones to respective first and second portions of said fluid spaced from each other in the direction of said axis of said conduit, and
• (f) sensing said first and second voltage drops across said first and second resistive means respectively.

A sensor for detecting a temperature difference, said sensor comprising:

• (a) a body of positive-temperature-coefficient material having a continuously-electrically-conductive first surface and a second surface which is discontinuously electrically conductive whereby to separate said second surface into a plurality of conductive zones,
• (b) means for electrically energizing said first surface,
• (c) a plurality of resistive means for connecting respective ones of said plurality of conductive zones to respective steady levels of potential whereby to elevate the respective temperatures of said plurality of conductive zones above the ambient level while developing voltage drops across said respective resistive means,
• (d) means for adjustably thermally coupling a first one of said plurality of conductive zones with a mechanical element having a temperature lower than that of said first one of said plurality of conductive zones, and
• (e) means for sensing said voltage drop across said resistive means connecting said first one of said plurality of conductive zones to its respective steady level of potential as a measure of said adjustable thermal coupling between said first one of said plurality of conductive zones and said mechanical element.