Spectrophotometer
First Claim
1. Non-dispersive spectrometric apparatus for detecting the presence of a first gaseous material despite the presence of a second gaseous material, said first gaseous material absorbing electromagnetic radiation at a relatively high rate at a first wavelength, said second gaseous material absorbing electromagnetic radiation at both said first wavelength and at a second wavelength, comprising:
- a source of electromagnetic radiation;
first and second photosensor means, said photosensor means being responsive to one of said first or said second wavelengths;
a chamber for receiving a sample to be tested for the presence of the first gaseous material, said chamber being disposed between said radiation source and said photosensor means;
first phosphor means disposed between said radiation source and said chamber for receiving radiation from said source and emitting in response thereto radiation at said first and said second wavelengths;
filter means disposed between said first photosensor means and said chamber for substantially attenuating radiation at that wavelength to which said photosensors are responsive, and passing the other of said wavelengths;
second phosphor means disposed between said first photosensor means and said filter means and responsive to said other of said wavelengths to produce radiation of the wavelength to which said photosensors are responsive; and
means coupled to said first and said second photosensor means for comparing the relative responses thereof to impingent radiation.
1 Assignment
0 Petitions
Accused Products
Abstract
An improved spectrophotometer of the non-dispersive absorption type useful for detecting the presence of SO2 in a gaseous sample, despite the simultaneous presence of NO2. Ultraviolet light from a commercially-available source impinges upon a fixed phosphor screen which fluoresces to produce ultraviolet radiation at a first wavelength, at which both SO2 and NO2 absorb radiation; and at a second wavelength at which absorption by SO2 is minimal but NO2 absorption is approximately the same as at the first wavelength. The radiation is directed through a sample chamber having windows which are transversely slidable to effect cleaning without destroying the integrity of the chamber seal, then introduced into an envelope enclosing filters and a pair of photosensors. One photosensor receives light at the second wavelength and produces a signal which reflects the attenuation by NO2 at that wavelength. The other sensor has disposed in front thereof a filter for blocking the second wavelength, and passing the first; and a phosphor for converting the passed (first) wavelength radiation into radiation at the second wavelength, which is then detected to produce a measure of the combined effect of NO2 and SO2. A comparison circuit then detects the differential between the first and second photosensors to determine the concentration of SO2. Means are provided to maintain the lamp, sample chamber and envelope at predetermined temperatures. A source of mercury vapor within the envelope saturates the interior of the envelope with the vapor for selectively attenuating undesired radiation at the 254 wavelength.
32 Citations
25 Claims
-
1. Non-dispersive spectrometric apparatus for detecting the presence of a first gaseous material despite the presence of a second gaseous material, said first gaseous material absorbing electromagnetic radiation at a relatively high rate at a first wavelength, said second gaseous material absorbing electromagnetic radiation at both said first wavelength and at a second wavelength, comprising:
-
a source of electromagnetic radiation; first and second photosensor means, said photosensor means being responsive to one of said first or said second wavelengths; a chamber for receiving a sample to be tested for the presence of the first gaseous material, said chamber being disposed between said radiation source and said photosensor means; first phosphor means disposed between said radiation source and said chamber for receiving radiation from said source and emitting in response thereto radiation at said first and said second wavelengths; filter means disposed between said first photosensor means and said chamber for substantially attenuating radiation at that wavelength to which said photosensors are responsive, and passing the other of said wavelengths; second phosphor means disposed between said first photosensor means and said filter means and responsive to said other of said wavelengths to produce radiation of the wavelength to which said photosensors are responsive; and means coupled to said first and said second photosensor means for comparing the relative responses thereof to impingent radiation. - View Dependent Claims (2, 3, 4, 5, 6, 7)
-
-
8. A non-dispersive spectrometer of the absorption type for detecting the presence of SO2 in a sample regardless of the simultaneous presence of NO2 comprising:
-
first and second photosensors responsive to ultraviolet light of a first wavelength; a source of ultraviolet light; a chamber disposed between said photosensors and said light source for receiving a sample to be analyzed for the presence of SO2, said chamber having windows transparent to ultraviolet light disposed at the ends thereof; a first phosphor element disposed between said light source and said chamber and responsive to said light source to emit ultraviolet light at said first and at a second wavelength; the SO2 exhibiting a relatively high degree of absorption at one of said first and second wavelengths and the NO2 exhibiting predictably proportioned degree of absorption at both said first and said second wavelengths; a filter disposed between said chamber and said first photosensor for attenuating light at said first wavelength and passing light at said second wavelength; a second phosphor element disposed between said filter and said first photosensor and responsive to light at said second wavelength to produce light at said first wavelength; and means coupled to said first and second photosensors for outputting a signal representative of the differential response thereof to impingent radiation. - View Dependent Claims (9, 10)
-
-
11. In a spectrophotometer including a chamber for receiving a gaseous sample to be analyzed, a source of radiation to be directed through said sample, and window means disposed in the walls of said chamber for allowing the passage of radiation therethrough, at least one of said window means comprising:
-
a frame extending generally transversely to the path of said radiation, said frame having an aperture therein to allow the passage of radiation; a window comprising an elongate pane of radiation-transparent material; said frame further comprising upper and lower guide means adapted to slidingly receive said pane whereby said pane may be displaced transversely with respect to said chamber so that an area of the pane in registry with said aperture may be succeeded by another area thereof; and gasket means disposed between said frame and said pane for substantially sealing the interior of said chamber during displacement of said pane. - View Dependent Claims (12, 13, 14, 15)
-
-
16. A spectrophotometer for the analysis of a sample by identification of the electromagnetic absorption qualities thereof, said spectrophotometer comprising:
-
a lamp for providing ultraviolet radiation; first heat responsive means in thermal communication with said lamp; a first heating element associated with said lamp; first control means coupled to said heat responsive means and said first heating element for maintaining said lamp at a predetermined temperature; a chamber for receiving a sample to be analyzed, said chamber having window means disposed at the ends thereof to allow ultraviolet radiation to pass through said chamber and said sample; second heat responsive means in thermal communication with said chamber; a second control means coupled to said second heat responsive means in said second heating element for maintaining said chamber at a predetermined temperature; a second heating element associated with said chamber; photosensor means responsive to ultraviolet radiation received from said chamber; an envelope surrounding said photosensor means; a third heating element associated with said envelope; and third control means coupled to said third heat responsive means and said third heating element for maintaining said envelope at a predetermined temperature. - View Dependent Claims (17, 18, 19)
-
-
20. A spectrophotometer for determining the presence of a specified gaseous material in a sample comprising:
-
a source of electromagnetic radiation producing radiation at desired wavelengths for analyzing the sample, and radiation at at least one additional undesired wavelength; photosensor means responsive to impingent radiation at a predetermined wavelength; a sample chamber intermediate said radiation source and said photosensor means and having window means therein for allowing radiation to traverse a sample within said chamber; an envelope enclosing said photosensor means; and a source of metallic vapor disposed within said envelope for saturating the interior of said envelope with said vapor, whereby said vapor selectively absorbs the radiation at said undesired wavelength. - View Dependent Claims (21, 22, 23, 24, 25)
-
Specification