Spectrophotometer

A non-dispersive spectrometer of the absorption type for detecting the presence of SO.sub.2 in a sample regardless of the simultaneous presence of NO.sub.2 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 SO.sub.2, 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 SO.sub.2 exhibiting a relatively high degree of absorption at one of said first and second wavelengths and the NO.sub.2 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.

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.

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.

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.