Fiber optic moisture analysis probe

• US 4,637,729 A
• Filed: 12/14/1983
• Issued: 01/20/1987
• Est. Priority Date: 12/14/1983
• Status: Expired due to Fees

• Current Assignee: Carrier Corporation (Carrier Global Corporation)
• Original Assignee: Carrier Corporation (Carrier Global Corporation)
• Inventors: Schoch, Stephen A.
• Primary Examiner(s): Evans, F. L.
• Assistant Examiner(s): Harringa, Joel L.
• Application Number:
  US06/561,409
• Time in Patent Office: 1,133 Days
• Field of Search: 250/227, 250/339, 250/373, 250/565, 356/408, 356/409, 356/410, 356/411, 356/434, 356/435, 356/40, 356/41, 356/402, 356/418, 356/432, 356/436, 356/320
• US Class Current: 356/410
• CPC Class Codes: G01N 21/314 with comparison of measurements at specific and non-specific wavelengths dual wavelength spectrometry G01J3/427
• CPC Class Codes: G01N 21/8507 Probe photometers, i.e. with optical measuring part dipped into fluid sample

Abstract

Light in two different wavelengths, only one of which is attenuated by the presence of a substance to be tested for, is passed through a light path which includes a fluid path. The two wavelengths are equally attenuated by particulate contamination and all other conditions except for the presence of the tested for substance. A light path through a reference cell provides a reference for each wavelength. The presence of the tested for substance provides a differential attenuation which is indicative of the presence of the substance and the degree of differential attenuation is a measure of the concentration of the substance.

Claims

1. A probe for detecting the presence of a substance in a fluid comprising:

first body means to be sealingly secured in the wall of a casing containing a fluid to be tested;

a passage through said first body means defining a flow path;

first mirror means forming a portion of said passage;

first optical fiber means having one end received in said first body means and defining a first termination which is located across said passage from said first mirror means and forming a portion of said passage;

said first optical fiber means having a second end defining a second termination;

second body means to be sealingly secured in the wall of a casing containing a fluid to be tested;

a sealed chamber in said second body means containing a reference medium;

means for equalizing pressure in said sealed chamber with the pressure acting on said second body means;

second mirror means forming a portion of said sealed chamber;

second optical fiber means having one end received in said second body means and defining a first termination which is located across said sealed chamber from said second mirror means and forming a portion of said sealed chamber;

said second optical fiber means having a second end defining a second termination;

means for supplying light in a first wavelength which is attenuated in the presence of said substance and in a second wavelength which is not attenuated in the presence of said substance such that said light traverses a first path serially including said first optical fiber means from said second termination to said first termination, across said flow path where said light in said first wavelength is subject to attenuation due to the presence of said substance whereupon said light is reflected by said first mirror means and said light in said first wavelength is subject to further attenuation due to the presence of said substance and depending upon the attenuation said light enters said first termination of said first optical fiber means, passes through said first optical fiber means and out said second termination of said first optical fiber means and for supplying light in said first and second wavelengths to a second path serially including said second optical fiber means from said second termination to said first termination, across said sealed chamber to said second mirror means whereupon said light is reflected by said second mirror means and enters said first termination of said second optical fiber means, passes through said second optical fiber means and out of said second termination of said second optical fiber means; and

means for detecting the amount of light in both of said wavelengths passing out of each of said second terminations.

2. The probe of claim 1 further including means for determining the difference in the amount of light in each of said wavelengths detected from each of said optical fiber means and for comparing the differences whereby an indication of the presence of the substance to be detected is obtained as well as an indication of the concentration thereof.

3. A probe for detecting the presence of a substance in a fluid comprising:

body means to be sealingly secured in the wall of a casing containing a fluid to be tested;

a passage through said body means defining a flow path therethrough;

a sealed chamber in said body means containing a reference medium;

means for equalizing the pressure of said reference medium with the pressure of the fluid to be tested;

mirror means in said passage and said sealed chamber and forming a portion thereof;

first optical fiber means having one end in said body means and defining a first termination which is located across said passage from said mirror means in said passage;

second optical fiber means having one end in said body means and defining a first termination which is located across said sealed chamber from said mirror means in said sealed chamber;

said first and second optical fiber means each having a second end defining a second termination;

means for supplying light in a first wavelength which is attenuated by said substance and in a second wavelength which is not attenuated in the presence of said substance;

said means for supplying light in said first and second wavelengths supplies said light in said first and second wavelengths to said first and second optical fiber means at said second terminations;

light supplied to said second termination of said first optical fiber means traverses a path serially including said first optical fiber means from said second termination to said first termination, across said flow path where said light in said first wavelength is subject to attenuation due to the presence of said substance whereupon said light is reflected by said mirror means in said passage and said light in said first wavelength is subject to further attenuation due to the presence of said substance and depending upon the attenuation said light enters said first termination, passes through said first optical fiber means and out said second termination;

light supplied to said second termination of said second optical fiber means traverses a path serially including said second optical fiber means from said second termination to said first termination, across said sealed chamber whereupon said light is reflected by said mirror means in said sealed chamber across said sealed chamber and enters said first termination, passes through said second optical fiber means and out said second termination;

means for detecting the amount of light in each of said wavelengths passing out of each of said second terminations; and

means for directing all of said light passing out of said second terminations onto said means for detecting.

4. The probe of claim 3 further including means for determining the difference in the amount of light in each of said wavelengths passing out of each of said paths and for comparing the differences whereby an indication of the presence of the substance to be detected is obtained as well as an indication of the concentration thereof.