FLUID ANALYZER APPARATUS

• US 3,677,652 A
• Filed: 06/15/1971
• Issued: 07/18/1972
• Est. Priority Date: 06/15/1971
• Status: Expired due to Term

• Current Assignee: John C. Little
• Original Assignee: John C. Little
• Inventors: Little, John C.
• Primary Examiner(s): Wibert, Ronald L.
• Assistant Examiner(s): Evans, F. L.
• Application Number:
  US05/057,417
• Time in Patent Office: 399 Days
• Field of Search: 250/43.5R,218,232,233 356/179-181,183,184,204-206,244,246,88,93-98
• US Class Current: 250/339.09
• CPC Class Codes: G01N 21/05 Flow-through cuvettes G01N21/09 takes precedence; handling fluid samples G01N1/10
• CPC Class Codes: G01N 30/74 Optical detectors measurement of intensity, velocity, spectral content, polarisation, or phase of infrared, visible or ultraviolet light G01J

Abstract

A hollow cell with opposed windows is connected in series with conduits through which automobile exhaust gas to be analyzed flows continuously. A broadband infrared source directs a beam through the windows to a first photodetector which measures the absorption of light at one wavelength to which one of the gas components, such as carbon monoxide (CO), is responsive. This beam is alternately directed over a longer path through the cell by a reflective chopper wheel adjacent the exit window and by mirrors mounted outside both windows to another photodetector which measures absorption of light at a different wavelength corresponding to another component, such as a hydrocarbon (HC). The outputs of both photodetectors are utilized to give continuous direct readout of the concentrations of the components. Each window is formed with a length of transparent plastic tape releasably sealed against the cell body and connected to a roll of the tape mounted adjacent to the cell. A clean window is provided by simply advancing a fresh length of tape into the cell and discarding the used portion.

Claims

1. A fluid analyzer comprising a cell having a hollow cell body and opposed end plates having windows, means for conducting fluid to and from said cell body, a source of light oriented to direct a beam into the cell through the window in one of the plates, a wheel mounted externally of the cell and having peripherally spaced reflective blades traversing at least part of the window in the other plate, means for rotating the wheel and causing light from the source alternately to pass between the blades and to be reflected by the blades back through the fluid in the cell, first photodetector means responsive to said light passing between the blades, second photodetector means responsive to light reflected by said blades, and utilization apparatus connected to said photodetectors.

2. The analyzer according to claim 1 with a mirror mounted over at least a portion of the window in said one plate for redirecting light reflected from said blades through the cell.

3. The analyzer according to claim 2 with a second mirror mounted over a portion of the window in said other plate and offset from the line of propagation from said source, said second mirror reflecting said light from the first named mirror into the cell, and means for adjusting the light reflecting angles of said wheel and said mirrors whereby selectively to vary the path length of light through the fluid in the cell.

4. The analyzer according to claim 1 in which said fluid comprises a gas mixture having at least two components with different spectral absorption characteristics, said first and second photodetector means having optical filters, respectively, with narrow bandpasses centered on the wavelengths corresponding to said absorption characteristics of said components.

5. The analyzer according to claim 4 with means for artifically producing attenuation of said beam equivalent to the attenuation thereof by predetermined concentrations of said components whereby to calibrate said utilization apparatus when a neutral gas sample is in said cell.