METHOD AND APPARATUS FOR MEASURING VAPOR PRESSURE

• US 3,856,404 A
• Filed: 06/06/1973
• Issued: 12/24/1974
• Est. Priority Date: 06/06/1973
• Status: Expired due to Term

• Current Assignee: Abe Hershler
• Original Assignee: Abe Hershler
• Inventors: Hershler, Abe
• Primary Examiner(s): Wibert, Ronald L.
• Assistant Examiner(s): Koren, Matthew W.
• Application Number:
  US05/367,612
• Time in Patent Office: 566 Days
• Field of Search: 356/36,37,38,201,244
• US Class Current: 356/36
• CPC Class Codes: G01N 21/49 within a body or fluid
• CPC Class Codes: G01N 21/552 Attenuated total reflection

Abstract

The relative vapor pressure of a gas is measured by exposing to the gas a sensor having a transparent substrate and a microcapillary porous surface and directing light into the substrate so that it is reflected one or more times from the porous layer as it traverses the substrate and measuring the emerging light as an indication of the relative vapor pressure. The microcapillary pores are unrestricted along their lengths, are of diameters between 100 and 400 Angstrom units and greater in depth than diameter and the microcapillary surface walls may be silane coated. The light is in the infrared, visible or ultraviolet range and is either ordinary or coherent. The light is measured by a photovoltaic or photoresistive cell either directly or in a bridge network with a vapor pressure insensitive light transmitter similar to the sensor and exposed to a common light source with the sensor. Where the gas is admixed with gasses of lower vapor pressure the lower vapor pressure gasses are first removed.

Claims

1. An apparatus for measuring the vapor pressure of a gas comprising a sensing member formed of a radiation transmissive material and having a plurality of microcapillary pores formed in a surface thereof with the inside faces of said pores being exposable to said gas, means for exposing said pores to radiation and radiation sensitive means responsive to a fraction of said radiation incident on said pores which fraction is responsive to the condensation of said gas on the faces of said pores as a function of said vapor pressure.

2. An apparatus for measuring the vapor pressure of a gas comprising a transparent sensing member having a plurality of microcapillary pores formed in a surface thereof, upon the faces of which pores said gas condenses as a function of said vapor pressure, means for providing light to a first section of the surface of said sensing member so that at least a portion thereof is incident on said pores, and light responsive means exposed to the light emerging from a second section of the surface of said sensing member.

3. The apparatus of claim 2 wherein said pores having diameters between 100 and 400 Angstrom units.

4. The apparatus of claim 3 wherein said pores have depths at least equal to their diameters.

5. The apparatus of claim 4 wherein said pores are unconstricted proximate their respective openings.

6. The apparatus of claIm 2 wherein the surfaces of said pores are silane coated.

7. The apparatus of claim 2 wherein said light responsive means comprises a photocell and including means for measuring a parameter of said photocell responsive to the light incident therein.

8. The apparatus of claim 2 wherein said sensing member comprises an elongated rod having said pores formed in a longitudinal face thereof and having light transmitting first and second faces at opposite ends thereof defining said first and second sections respectively.

9. The apparatus of claim 8 including a standard member defining transparent second rod having opposite first and second light transmitting faces, said light means comprising a common light source exposed to the first faces of said sensing and standard members, said light responsive means comprising a pair of photocells exposed to the light emerging from said second faces and means for measuring a relationship of a parameter of said photocells responsive to the light incident thereon.

10. The apparatus of claim 8 including a plurality of said sensing members spaced from and parallel to each other, the first faces thereof being exposed to said light and said light responsive means being exposed to the light emerging from said second faces.

11. The apparatus of claim 8 including means for masking a predetermined area of said first face.

13. The sensor of claim 12 wherein said pores are unconstricted proximate the open ends thereof.

14. The sensor of claim 13 wherein the surfaces of said pores are silane coated.

15. The method of measuring the vapor pressure of a gas comprising exposing the inside faces of a plurality of microcapillaries to said gas, exposing said microcapillaries to radiation and measuring said radiation after exposure to said microcapillaries as an indication of said vapor pressure.

16. The method of claim 15 wherein said micracapillaries have widths between 100 and 400 Angstrom units.

17. The method of claim 15 wherein said microcapillaries are unconstricted along the lengths thereof.

18. The method of claim 15 wherein said microcapillaries are formed in a radiation transmitting substrate and said optical measurement comprises exposing said substrate to said radiation to direct at least a portion thereof through said substrate onto the faces of said microcapillaries and measuring said radiation which is a function thereof dissipated at said microcapillary faces.

19. The method of claim 15 wherein said microcapillaries are formed in a surface layer of a transparent substrate exposed to said gas, said microcapillaries having diameters between 100 and 400 Angstrom units and lengths exceeding said diameters and said measurement comprises directing light into said substrate with at least a portion thereof being incident on said surface layer and measuring the value of said light which is a function of the dissipation thereof at said surface layer.

20. The method of claim 19 wherein the value of said light reflected from said surface layer and emerging from said substrate is measured.

21. The method of claim 15 wherein said gas is contained in a mixture of gasses and has a lower vapor pressure than the other gasses in said mixture.

22. The method of claim 15 wherein said gas comprises water vapor.

23. The method of claim 15 wherein said gas comprises water vapor and the singularity temperature of said vapor pressure is measured as the dew point.