VISUAL-TYPE HYGROMETER

• US 3,776,038 A
• Filed: 04/06/1972
• Issued: 12/04/1973
• Est. Priority Date: 04/06/1972
• Status: Expired due to Term

• Current Assignee: Stanley B. Elliott
• Original Assignee: Stanley B. Elliott
• Inventors: Elliott, Stanley B.
• Primary Examiner(s): Queisser, Richard C.
• Assistant Examiner(s): Corr, Denis E.
• Application Number:
  US05/241,573
• Time in Patent Office: 607 Days
• Field of Search: 73/335,336.5,29 350/157,158 116/114AM
• US Class Current: 73/335.01
• CPC Class Codes: G01N 21/81 Indicating humidity

Abstract

A visual type hygrometer including (1) a source of illumination that provides a light beam, (2) means for providing observable changes in relative humidity which is a chemical composition such as the sodium salt of 1,1'"'"''"'"' binaphthyl 8-8'"'"''"'"' dicarboxylic acid that of itself senses changes in relative humidity by being abruptly triggered at a predetermined relative humidity, and (3) light detecting means for detecting observable changes in the brightness and intensity of the light coming from the composition when the light beam contacts the composition.

Claims

2. A device as defined in claim 1 in which the composition is birefringent at the first relative humidity when hydrated and non-birefringent at the second relative humidity when less hydrated.

3. A device as defined in claim 1 in which the composition is birefringent at the first relative humidity when solid and non-birefringent at the second relative humidity when liquid.

4. A device as defined in claim 1 in which the means for providing observable changes includes means to intensify observable changes comprising a polarizer for polarizing the light beam and an analyzer for analyzIng the beam, the light beam traveling through the device by going through the polarizer and the polarized light passing through the composition that doubly refracts the beam when birefringent at the first relative humidity to pass the beam on through the analyzer.

5. A device as defined in claim 1 in which the composition is translucent at the first relative humidity and transparent at the second relative humidity.

6. A device as defined in claim 5 in which the composition is translucent at the first relative humidity when hydrated and transparent at the second relative humidity when less hydrated.

7. A device as defined in claim 5 in which the composition is translucent at the first relative humidity when solid and transparent at the second relative humidity when liquid.

8. A device as defined in claim 1 in which the means for providing observable changes includes means for illuminating the composition which when translucent at the first relative humidity provides light of sufficient intensity and brightness to provide a visual signal.

9. A device as defined in claim 1 in which the light detecting means includes electrical means responsive to the visual signal at the first relative humidity and non-responsive to the signal at the second relative humidity.

10. A device as defined in claim 9 in which the electrical means includes a photo-responsive solid state electronic device.

11. A device as defined in claim 9 in which there is electrical control means responsive to the electrical means that is responsive to the visual signal, the control means for controlling electrical power to activate an electrical circuit.

12. A hygrometer as defined in claim 1 in which the composition comprises a compound having at least two rings in its structure and at least one polar group whose alkali salts furnish ions to hydrate.

13. A hygrometer as defined in claim 12 in which the polar group is a member selected from the group consisting of hydroxyl, carboxyl and sulfonic radicals.

14. A hygrometer as defined in claim 1 in which the composition comprises a compound having at least two benzene rings in its structure and polar groups whose mixed alkali metal salts furnish ions to hydrate.

15. A method of measuring relative humidity with a visual-type hygrometer comprising the steps of:

(1) providing a light beam from a source of illumination, (2) contacting with the light beam a chemical composition that of itself senses changes in relative humidity and that is anisotropic and translucent at a first relative humidity and isotropic and clear at a second relative humidity, (3) sensing changes in the light coming from the composition that are due to changes in relative humidity in which the light from the composition at the first relative humidity is of sufficient brightness and intensity to provide a visual signal at the first relative humidity but not at the second relative humidity.

16. A method as defined in claim 15 in which there is provided the steps of polarizing the light beam before contacting the composition, doubly refracting the polarized light beam at the first relative humidity when the composition is contacted, and analyzing the doubly refracted light beam passing through the composition.

17. A method as defined in claim 16 in which the composition is birefringent and doubly refracts the polarized beam at the first relative humidity when hydrated and does not doubly refract the polarized beam at the second relative humidity when less hydrated.

18. A method as defined in claim 16 in which the composition doubly refracts the polarized beam when solid at the first relative humidity and does not doubly refract the beam when in solution at the second relative humidity.

19. An electrical-type hygrometer device comprising optical means for moving a light beam through the device, means for polarizing the light beam, means for analyzing the light beam, a chemical composition that of itself senses changes in relative humiDity, the composition doubly refracting the light beam at a first relative humidity to pass the light beam through the device, and not doubly refracting the beam at a second relative humidity so that the light beam does not pass through the device, and electrical means responsive to the passing of the light beam through the composition at the first relative humidity to provide an electrical response to a change in relative humidity.

20. A device as defined in claim 19 in which there is provided electrical control means for controlling electrical power to activate an electrical circuit, the electrical control means being responsive to the light-detecting electrical means.

21. An electrical-type hygrometer comprising:

(1) a source of illumination providing a light beam, (2) means for providing observable changes in relative humidity comprising a chemical composition that itself senses changes in relative humidity, the composition being anisotropic and translucent at a first relative humidity and isotropic and clear at a second relative humidity, and (3) light-detecting electrical means responsive to observable changes in the brightness and intensity of the light coming from the composition, the light coming from the composition at the first relative humidity being of sufficient brightness and intensity to provide a visual signal to activate the light-detecting electrical means.

22. A method of measuring relative humidity with an electrical-type hygrometer device comprising the steps of:

(1) providing a light beam from a source of illumination, (2) contacting with the light beam means for providing observable changes in relative humidity, including a chemical composition that is responsive to changes in relative humidity and that is anisotropic and translucent at a first relative humidity and isotropic and clear at a second relative humidity, and (3) detecting changes in the light coming from the composition that are due to changes in relative humidity with light-detecting electrical means in which the light coming from the composition at the first relative humidity is of sufficient brightness and intensity to provide a signal.

23. A visual-type hygrometer comprising:

(1) a source of illumination providing a light beam, (2) a chemical composition that of itself senses changes in relative humidity, the composition being birefringent at a first relative humidity and non-birefringent at a second relative humidity, (3) means to amplify observable changes in the composition due to changes in relative humidity including a polarizer for the light beam and an analyzer for the polarized beam that is passed through the composition, and (4) light detecting means for detecting changes in the brightness and intensity of light coming from the composition because of changes in relative humidity.

24. A hygrometer as defined in claim 23 in which the hygrometer is a transmission type in which the light beam passes through the polarizer and the polarized light beam passes through the composition, where it is doubly refracted at the first relative humidity, and the emerging refracted beam passes through the analyzer.

25. A hygrometer as defined in claim 23 in which the hygrometer is a reflective-type, the light beam passing through the polarizer and the chemical composition to a mirror and then being reflected back through the composition and the analyzer.

26. A hygrometer as defined in claim 23 in which the composition is located between the polarizer and the analyzer.

27. A hygrometer as defined in claim 23 in which the composition comprises an alkali metal salt of 1,1,3-trimethyl-5-carboxy-3-(p-carboxy phenyl) indan.

28. A hygrometer as defined in claim 23 in which the composition comprises an alkali metal salt of 3,3'"'"''"'"',4,4'"'"''"'"'-benzophenone tetracarboxylic dianhydride.

29. A hygrometer as defined in claim 23 in which the composition comprises an alkali metal salt of 1,1'"'"''"'"' binaphthyl 8-8'"'"''"'"' dicarboxylic acid.

30. A hygrometer as defined in claim 23 in which the composition comprises an alkali metal salt of naphthochrome green.

31. A hygrometer as defined in claim 23 in which the composition is a coating on a transparent substrate.

32. A hygrometer as defined in claim 23 in which the composition is a coating on a translucent substrate.

33. A hygrometer as defined in claim 23 in which the composition is a coating on a transparent or translucent substantially isotropic substrate.

34. A hygrometer as defined in claim 33 in which the thickness of the coating is at least about 0.01 milimeter.

35. A hygrometer as defined in claim 23 in which the composition includes an inorganic compound having a high surface area.

36. A hygrometer as defined in claim 23 in which at least two discrete areas which are adjacent in the same plane or optically spaced in parallel planes are occupied with compositions comprising a series of compounds or mixtures of compounds whose birefringence terminates at different relative humidities.

37. A hygrometer as defined in claim 36 in which the series of compounds includes potassium salts of levalinic acid, phthalic acid, succinic acid, adipic acid, 1,2,4,5-benzenetetracarboxylic acid, fumaric acid and o-benzoyl benzoic acid.

38. A hygrometer as defined in claim 36 in which the series of compounds includes the dipotassium salt of tetrahydrophthalic acid, the sodium salt of 4-chlorophthalic acid, and the tetrasodium salt of 1,2,4,5-benzene tetracarboxylic acid.

39. A hygrometer as defined in claim 23 in which the polarizer is a circular-type and the polarized light beam passes through the composition to a mirror and is reflected back through the composition to the analyzer.

40. A method of measuring relative humidity by a visual-type hygrometer comprising the steps of:

(1) providing a light beam from a source of illumination, (2) polarizing the light beam, (3) passing the polarized light beam through a chemical composition that of itself senses changes in relative humidity, the composition being birefringent at a first relative humidity and non-birefringent at a second relative humidity, (4) doubly refracting the light beam with the composition that is birefringent at the first relative humidity, but not doubly refracting the beam at the second relative humidity, (5) analyzing the doubly refracted light beam passing through the composition at the first relative humidity, and (6) observing the analyzed light beam of step (5) that is of sufficient brightness and intensity to provide a visual signal at the first relative humidity but not at the second relative humidity.

41. A visual-type hygrometer comprising a polarizer for a light beam, an analyzer for the light beam, and a chemical composition that refracts the light beam before being analyzed, the composition containing a compound that is responsive to changes in relative humidity by doubly refracting the light beam at a first relative humidity when hydrated and non-birefringent at a second relative humidity when less hydrated.

42. A hygrometer as defined in claim 41 in which the composition is adapted to undergo at least about 100 cycles of birefringence and non-birefringence.

43. A hygrometer as defined in claim 41 in which the composition is adapted to undergo at least one cycle from non-birefringent to birefringent but which becomes irreversibly birefringent if the birefringent state is maintained longer than approximately 72 hours.

44. A visual-type hygrometer comprising a polarizer for a light beam, an analyzer for the light beam, and a chemical composition that refracts the beam before being analyzed, the composition containing a compound that is responsive to changes in relative humidity, the compound being birefringent at a first relative humidity when solid and non-birefringent at a second relative humidity when in solution.

45. A hygrometEr as defined in claim 44 in which the saturated solution of the composition has a vapor pressure in the range of about 1 to 17.5 mm of mercury at 68* F.

46. A hygrometer as defined in claim 44 in which the composition includes a potassium salt of o-benzoyl benzoic acid.

47. A hygrometer as defined in claim 44 in which a substrate containing at least two chemical compositions is located between the polarizer and the analyzer, a first chemical composition being birefringent at a first relative humidity and non-birefringent at a second relative humidity, and a second chemical composition that is birefringent at a third relative humidity and non-birefringent at a fourth relative humidity.

48. A method of measuring humidity by a visual-type hygrometer including a polarizer for a light beam and an analyzer for the light beam, the method comprising the steps of providing a chemical composition that refracts the light beam, the composition being responsive to changes in relative humidity by doubly refracting the light beam at a first relative humidity when hydrated and not doubly refracting the light beam at a second relative humidity when less hydrated, and passing the light beam, before being analyzed, through the chemical composition to doubly refract the beam at the first relative humidity to provide a visual indication of a change in relative humidity.

49. A method of measuring humidity by a visual-type hygrometer including a polarizer for a light beam, an analyzer for the light beam, and a chemical composition that refracts the beam being analyzed, the composition containing a compound that of itself senses changes in relative humidity, the compound being birefringent at a first relative humidity when solid and non-birefringent at a second relative humidity when in solution, the method comprising passing the light beam through the chemical comosition to doubly refract the beam at the first relative humidity, and passing the light beam through the chemical composition at the second relative humidity to not doubly refract the beam and provide visual indication of a difference in humidity between the first and second relative humidities.