Temperature sensing device

• US 4,179,927 A
• Filed: 09/28/1977
• Issued: 12/25/1979
• Est. Priority Date: 09/28/1977
• Status: Expired due to Term

• Current Assignee: Electric Power Research Institute Incorporated
• Original Assignee: Electric Power Research Institute Incorporated
• Inventors: Saaski, Elric W.
• Primary Examiner(s): Swisher, S. Clement
• Assistant Examiner(s): Corr, Denis E.
• Application Number:
  US05/837,451
• Time in Patent Office: 818 Days
• Field of Search: 73/356, 73/339 R, 73/350, 250/231 R
• US Class Current: 374/152
• CPC Class Codes: G01K 1/024 for remote indication
• CPC Class Codes: G01K 11/14 of inorganic materials
• CPC Class Codes: G01K 11/18 of materials which change translucency

Abstract

A device for sensing temperature changes at an object, specifically within a transformer or the like, is disclosed herein. This device utilizes an electrically non-conductive sensor including a temperature responsive substance having the characteristic of changing in optical density with changes in temperature. In order to detect changes and/or to actually monitor the temperature the device provides means for detecting and/or monitoring the optical density of the temperature responsive means, thereby indicating the temperature at the object.

Claims

1. A device for sensing temperature changes at an object, comprising:

(a) a sensor including electrically non-conductive temperature responsive media which changes in optical density with changes in temperature, said media including the combination of gaseous NO₂ and gaseous N₂ O₄ the proportion of each depending upon the temperature at said sensor, said combination having constant total mass density, said sensor being adapted for positioning adjacent said object, whereby changes in temperature at said object changes the proportions of said gases and optical density of said media and therefore the light absorption characteristic of said media, and

(b) means for detecting changes in optical density of said temperature responsive media, thereby indicating changes in temperature at said object, said detecting means including

(i) first means for directing a predetermined amount of light from a light source into said temperature responsive media, and

(ii) second means for detecting the amount of light not absorbed by said temperature responsive media, whereby a change in temperature at said object will change the amount of light detected by said second means.

2. A device according to claim 1 wherein said first means includes a fiber optics bundle adapted to direct light from said light source to said object.

3. A device according to claim 1 wherein said second means includes a fiber optics bundle adapted to direct said detected light from said temperature responsive media to a remote location.

4. A device according to claim 1 wherein said sensor includes a sealed envelope for housing said temperature responsive media, said envelope including a section at one end thereof, which section is capable of passing light therethrough, and a light reflecting surface at an opposite end thereof, said light reflecting surface facing said section.

5. A device according to claim 4 wherein said light passing section is transparent to light.

6. A device for sensing temperature changes at a predetermined point within an object, comprising:

(a) a sensor consisting of a gaseous combination of NO₂ and N₂ O₄ which changes in optical density with changes in temperature, said combination having constant total mass density, said sensor being adapted for positioning at said predetermined point, whereby changes in temperature at said predetermined point changes the optical density and therefore the light absorption characteristic of said gaseous combination;

(b) a light source located at a remote location relative to said point;

(c) a first fiber optics bundle extending from said light source to a first fixed point at said sensor for directing a predetermined amount of light into said gaseous combination; and

(d) a second fiber optics bundle extending from a second fixed point at said sensor to a remote location for detecting the amount of light not absorbed by said gaseous combination and transmitting said detected light to said location, whereby a change in temperature at said predetermined point will change the amount of light detected and transmitted by said second fiber optics bundle.

7. A device according to claim 6 wherein said sensor includes a sealed envelope for housing said gaseous combination, said envelope including a section at one end thereof, which section is capable of passing light therethrough, and a light reflecting surface located at the other end and facing said light passing section, said fiber optics bundles having adjacent ends located at said light passing section of said envelope, whereby light from said first bundle enters said gaseous substance through said section and whereby that light not absorbed is reflected back to said second bundle by said reflector means through said light passing section.

8. A device according to claim 7 wherein said light passing section is transparent to light.

9. A device according to claim 6 including means for converting the light detected by said second bundle to an electrical signal and for treating the signal so that it is indicative of the relative temperature at said predetermined point.

10. A device for monitoring temperature at a predetermined point within electric and magnetic fields in a transformer, said device comprising:

(a) a non-metallic sensor located at said predetermined point, said sensor including

(i) a sealed envelope one end of which has a light transparent section and an opposite end of which has a light reflective surface facing said light transparent section, and

(ii) a gaseous substance located within said envelope, said gaseous substance being of the type which changes proportionately in optical density with changes in temperature, whereby changes in temperature at said predetermined point within said transformer proportionately changes the optical density and therefore the light absorption characteristic of said gaseous substance;

(b) a light source in the form of a light emitting diode located outside said transformer;

(c) a first fiber optics bundle having one end located adjacent said light source and its opposite end located at the light transparent section of said envelope, whereby light from said source is directed into said envelope and through said gaseous substance towards said reflective surface such that any light not absorbed by said gaseous substance is reflected back toward said section, whereby said unabsorbed light is proportionate to the optical density of said gaseous substance and therefore the temperature at said point;

(d) electrical circuit means including a phototransistor for converting a light signal to a corresponding electrical signal; and

(e) a second fiber optics bundle having one end located at said circuit means and its opposite end located at said light transparent section, whereby any of said light which is not absorbed by said gaseous substance and which passes out of said transparent section is directed to said circuit means for conversion to an electrical signal whereby said signal is proportionate to said light and therefore the temperature at said point; and

(f) means for treating said signal so as to indicate the actual temperature at said predetermined point, said treating means including a DC bridge circuit including said phototransistor connected in one leg of said bridge, a second phototransistor connected in a second leg of said bridge, said second phototransistor being positioned to receive light directly from said light emitting diode.

11. A device according to claim 10 wherein said gas includes NO₂ and N₂ O₄.

12. A device according to claim 10 wherein said sensor is a miniaturized sensor.

13. A device for sensing temperature changes at a predetermined point, comprising:

(a) a sensor including electrically non-conductive temperature responsive media which changes in optical density with changes in temperature, said media being adapted for positioning at said point, whereby changes in temperature at said point changes the optical density of said media; and

(b) means for detecting changes in optical density of said temperature responsive media, thereby indicating changes in temperature at said point, said detecting means including

(i) a light source located at a remote location relative to said point,

(ii) first means for directing a predetermined amount of light from said source into said temperature responsive media, and

(iii) second means for detecting the amount of light not absorbed by said temperature responsive media and for producing an electrical signal in response thereto, said second means including a DC bridge circuit including one photosensitive electrical device connected in one leg of the bridge circuit and a second photosensitive electrical device connected in a second leg of the bridge, said second photosensitive electrical device being positioned to receive light directly from said light source.