Condensation particle counter false count performance
Various embodiments include methods of reducing false-particle counts in a water-based condensation particle counter (CPC). One embodiment of a method includes delivering water into one or more wicks, sensing an excess volume of water delivered to the wicks, collecting the excess volume of water into a collection reservoir, and draining the excess volume of water from the collection reservoir. Other methods and apparatuses are disclosed.
1. A method of reducing false-particle counts in a water-based condensation particle counter (CPC), the method comprising:
delivering water into a plurality of wicks, each of the plurality of wicks being formed from a porous media material with an open portion formed therethrough along a length of the wick, the open portion forming an inner diameter of respective ones of the plurality of wicks for directing a separate aerosol sample flow within respective ones of each of the plurality of wicks, the plurality of wicks being substantially parallel and adjacent to one another within the water-based CPC and extending from a wick stand on a first end of the plurality of wicks to a flow joiner on a second end of the plurality of wicks, the flow joiner for combining particles from the aerosol sample flows from the plurality of wicks into a single aerosol stream immediately prior to a particle detection chamber within the CPC, each of the plurality of wicks for transporting separate portions of the delivered water;
sensing an excess volume of water delivered to the plurality of wicks;
collecting the excess volume of water into a collection reservoir; and
draining the excess volume of water from the collection reservoir.
2. The method of claim 1 , further comprising pulling a constant air flow through an exhaust-air port to drain the excess volume of water.
3. The method of claim 1 , further comprising detecting when a drain is filled with water to a predetermined level.
4. The method of claim 1 , further comprising draining the excess water volume by pumping the excess water volume.
5. The method of claim 1 , further comprising applying a digital filter to further reduce false-particle counts.
6. The method of claim 1 , further comprising comparing detected particle counts with a look-up table to subtract false-particle counts.
7. The method of claim 6 , further comprising constructing the look-up table by storing signatures of detected signals produced by known false-particles.
8. A system to reduce false-particle counts in a water-based condensation particle counter (CPC), the system comprising:
an aerosol sample inlet configured to be coupled to a sample flow pump;
a plurality of wicks to receive water, each of the plurality of wicks being formed from a porous media material with an open portion formed therethrough along a length of the wick, the open portion forming an inner diameter of respective ones of the plurality of wicks and being configured to direct a separate aerosol sample flow within each of the plurality of wicks, the plurality of wicks being substantially parallel and adjacent to one another within the water-based CPC from a wick stand coupled to the aerosol sample inlet on a first end of the plurality of wicks to a flow joiner coupled to the sample flow pump on a second end of the plurality of wicks, the flow joiner configured to combine particles from the aerosol sample flow within each of the plurality of wicks into a single aerosol stream immediately prior to a particle detection chamber within the CPC, each of the plurality of wicks being configured to transport separate portions of the received water;
a collection reservoir to collect an excess volume of water from the plurality of wicks; and
a sensor to provide a signal corresponding to the excess volume of water in the plurality of wicks.
9. The system of claim 8 , further comprising a water drain port coupled to the collection reservoir to remove excess water.
10. The system of claim 8 , wherein the plurality of wicks is field replaceable by an end-user of the CPC.
11. The system of claim 8 , wherein the sensor is to detect when the collection reservoir is filled with water to a predetermined level.
12. The system of claim 8 , further comprising a digital filter to further reduce the false-particle counts.
13. The system of claim 12 , wherein the digital filter is to compare detected particle counts with a look-up table to subtract false-particle counts.
14. The system of claim 13 , wherein the look-up table includes a plurality of stored signatures of detected signals produced by known false-particles.
15. The system of claim 8 , wherein the plurality of wicks is silver impregnated to reduce or prevent bacterial growth within the plurality of wicks.
16. The system of claim 8 , wherein the plurality of wicks is treated with a bio-inhibitor to reduce or prevent bacterial growth within the plurality of wicks.
17. The system of claim 8 , further comprising a removable wick cartridge coupled to the wick stand onto which the plurality of wicks is mounted, the removable wick cartridge configured to be heated to reduce or eliminate effects from varying levels of relative humidity, thereby reducing or eliminating bubbles or empty water droplets due to elevated levels of relative humidity.
18. A system to reduce false-particle counts in a water-based condensation particle counter (CPC), the system comprising:
an aerosol sample inlet configured to be coupled to a sample flow pump;
a single wick to receive water, the single wick being a porous media having multiple separate aerosol flow paths formed therethrough along a length of the single wick, each of the multiple separate aerosol flow paths being surrounded along a length of the path by the porous media with each comprising an open portion being configured to direct an aerosol sample flow therein, each of the multiple separate aerosol flow paths being substantially parallel and adjacent to one another within the water-based CPC from a wick stand coupled to the aerosol sample inlet on a first end of the single wick to a flow joiner coupled to the sample flow pump on a second end of the single wick, the flow joiner configured to combine particles from the multiple separate aerosol flow paths into a single aerosol stream immediately prior to a particle detection chamber within the CPC, the single wick being configured to transport separate portions of the received water; and
a collection reservoir to collect the excess volume of water from the single wick.
19. The system of claim 18 , further comprising a sensor to make a determination whether an excess volume of water is delivered to the single wick.
20. The system of claim 19 , wherein the sensor includes one or more sensors selected from various types of sensors including a water sensor, a temperature sensing device, and a humidity sensing device, the sensor being configured to generate a signal to stop a supply of water sent to the single wick.