Measuring and testing – Sampler – sample handling – etc. – Automatic control
Reexamination Certificate
2001-03-08
2003-07-01
Noland, Thomas P. (Department: 2856)
Measuring and testing
Sampler, sample handling, etc.
Automatic control
C073S863230
Reexamination Certificate
active
06584865
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an aerosol sampler system. More particularly, the aerosol sampler system of the present invention provides an aerosol sampling that does not disturb the environment upstream of the collected sample. Most particularly, the aerosol sampler system collects aerosol samples in an unbiased manner with respect to aerosol particle size.
2. Brief Description of the Related Art
Sample size bias occurs within most commercially available sample collection systems. This is most commonly a result of the competition between air drag and inertial effects on the aerosol particle due to non-uniformities in the airflow at the entrance of the sample collection system. This problem is addressed by assigning a parameter known as aerodynamic equivalent diameter (AED) which equates a given particle to that of a theoretical spherical particle with a specific standard density, i.e., the theoretical spherical particle displays an experimental aerodynamic behavior that is the same as the real given particle. As such, the particle size is equated with the “aerodynamic equivalent diameter,” i.e., the size of a unit density sphere having the same settling velocity as the particle in question, of whatever size, shape or density. Simply viewed, as the flow into a collection entrance becomes increasingly restricted, less massive particles are proportionately forced around the entrance, while the particles having a greater mass are more disproportionately forced into the entrance, resulting in sampling errors.
The currently available sampling devices introduce biasing factors into the collected sample, due to various imperfections and limitations in their design. These samplers generally fall into two categories, omni-directional samplers and fixed direction samplers. Omni-directional samplers generally under-sample larger particle sizes (>10 microns), as the larger particles tend to deviate from the air stream direction due to inertial effects when entering the inlet, resulting in impaction on the inner walls of the inlet. Further complicating the collection process is the fact that the magnitude of the loss of large particles is a function of the ambient wind speed. Similarly, fixed directional samplers generally under-sample larger particles when not aligned with the ambient wind direction, or when sampling at an inlet velocity greater than that of the ambient wind speed. The magnitude of these losses is also a function of wind speed. As a result, even when these sampling flaws are apparent for a given experiment, the affect of these flaws on the collected sample remains unknown.
Accordingly, there is a need to provide an improved aerosol sampling system that collects aerosol samples in an unbiased manner with respect to aerosol particle size. The present invention addresses this and other needs.
SUMMARY OF THE INVENTION
The present invention includes an absolute reference sampler system comprising (A) a positioning component comprising a sampling head having a collection inlet, means for determining wind direction wherein the wind direction is determined in real time, means for comparing the position of the collection inlet and the determined wind direction wherein a differential value is created and means for positioning the sampling head reactive to the differential value and operably connected to the sampling head wherein the means for positioning the sampling head rotates the sampling head for isoaxial alignment with the determined wind direction, and (B) an intake component comprising a mass flow controller, means for determining wind speed wherein the wind speed is determined in real time and means for drawing an effective amount of ambient air into the collection inlet for mass flow controller operation wherein the mass flow controller receives an input for the determined wind speed causing the mass flow controller to regulate ambient air flow into the collection inlet to an air speed substantially equivalent to the determined wind speed.
The present invention also includes a method for ambient aerosol sampling comprising the steps of providing an absolute reference sampler system comprising (A) a positioning component comprising a sampling head having a collection inlet, means for determining wind direction wherein the wind direction is determined in real time, means for comparing the position of the collection inlet and the determined wind direction wherein a differential value is created and means for positioning the sampling head reactive to the differential value and operably connected to the sampling head wherein the means for positioning the sampling head rotates the sampling head for isoaxial alignment with the determined wind direction, and (B) an intake component comprising a mass flow controller, means for determining wind speed wherein the wind speed is determined in real time and means for drawing an effective amount of ambient air into the collection inlet for mass flow controller operation wherein the mass flow controller receives an input for the determined wind speed causing the mass flow controller to regulate ambient air flow into the collection inlet to a speed substantially equivalent to the determined wind speed, and drawing an effective amount of ambient air into the collection inlet wherein the differential value relative to the wind direction and sampling head position is calculated causing the means for. positioning the sampling head to rotate the sampling head proportionally to the differential value to a calculated position and wherein the mass flow controller regulates the ambient air flow into the collection inlet to a speed substantially equivalent to the determined wind speed.
The present invention further includes an ambient aerosol sampling product generated by the process comprising the steps of positioning a collection inlet into isoaxial alignment with a determined wind direction in real time and regulating ambient air flow into the collection inlet to a speed substantially equivalent to a determined wind speed in real time wherein an amount of collected aerosol comprises an unbiased environmental sample.
The present invention isoaxially aligns the collection inlet of the aerosol sampling system with the wind direction and draws an isokinetic sample at an inlet speed equivalent to the wind speed, allowing the collection of an unbiased aerosol sample with respect to aerosol particle size.
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DeLuca Paul J.
Doherty Robert W.
Biffoni Ulysses John
Noland Thomas P.
The United States of America as represented by the Secretary of
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