Various embodiments include composite wicks for ultra-low noise condensation particle counters (CPCs). In one embodiment, a composite wick includes a first porous material having a first pore density, with the first porous material further having a first surface and an opposing second surface. A second porous material is in fluid communication with the first porous material and has a first surface with an area substantially the same as an area of the first surface of the first porous material. The first surface of the second porous material is substantially in contact with the first surface of the first porous material. The second porous material has a pore density that is dissimilar the first pore density of the first material. The first material and the second material are configured to provide vapor from a liquid to a fluid-based particle counter. Other apparatuses are disclosed.

The invention relates to a method (200) and an apparatus (110) for determining a concentration of aerosol particles (112) in a carrier gas (114), in particular for examining atmospheric aerosols (118) or as aerosol particle detector in process gases or in clean air rooms. The method (200) here comprises the steps: a) provision of an aerosol (118) which has aerosol particles (112) in a carrier gas (114) comprising at least one condensable component; b) introduction of at least part of the aerosol (118) into a chamber (120) of a pressure-rated vessel (116), wherein the chamber (120) is delimited by at least one wall (128), wherein the at least one wall (128) adjoining the chamber (120) is set to a temperature which is above a saturation temperature of at least one condensable component; c) subsequent removal of part of the aerosol (118) from the chamber (120), as a result of which a decrease in pressure in the chamber (120) occurs, as a result of which the at least one condensable component condenses at least partly on the aerosol particles (112); and d) determination of a concentration of aerosol particles (112) in the carrier gas (114) during removal of the part of the aerosol (118) from the chamber (120).

The invention can be suitable, in particular, for examining atmospheric aerosols, in particular aerosol particles, but can also be used as aerosol particle detector in process gases or in clean air rooms.

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.

A measurement system includes an atomizer, an impactor, a particle counter, and a discharge reservoir. The atomizer has a liquid intake port and a gas intake port configured to aerosolize a liquid received at the liquid intake port. The impactor has an inlet coupled to the atomizer and has a first output port and a second output port. The impactor is configured to separate droplets wherein those droplets smaller than a selected cut point are directed to the first output port and those droplets larger than the selected cut point are directed to the second output port. The particle counter is coupled to the first output port and is configured to count particles larger than at least one particle size cut point. The discharge reservoir is coupled to the second output port.

A distribution unit of a particle detection system initiates a particle collection process to dislodge one or more surface particles from a surface of an article based on a stream including at least one of solid CO.sub.2 particles or CO.sub.2 droplets. The dislodged surface particles are collected on a surface of a substrate having a pre-determined initial state including initial surface particles of the substrate. A measurement indicating a particle number concentration of detectable surface particles on the substrate after the particle collection process is completed is obtained. An initial particle number concentration of the initial surface particles of the pre-determined initial state is identified. A number of particles transported away from the surface of the article is determined based on the obtained measurement and the identified initial particle concentration.

The disclosed subject matter compensates or corrects for errors that otherwise would be present when a measurement is made on a condensation particle counting system with the only difference causing the errors being absolute pressure. The difference in absolute pressure may be due to, for example, a change in altitude in which the condensation particle counting system is located. Techniques and mechanisms are disclosed to compensate for changes in particle count, at a given particle diameter, for changes in sampled absolute pressure at which measurements are taken. Other methods and apparatuses are disclosed.

Methods and systems are provided for a PM sensor. In one example, a method comprises flowing exhaust gas to a cone-shaped PM sensor having a pair of openings arranged across from one another and a plurality of outlets distal to the pair of openings.

Various embodiments include methods and apparatuses to reduce false-particle counts in a water-based condensation particle counter (CPC). In one embodiment, a cleanroom CPC has three parallel growth tube assemblies. A detector is coupled to an outlet of each of the three parallel growth tube assemblies, and is used to compare the particle concentrations measured from each of the three growth tube assemblies. An algorithm compares the counts from the three detectors and determines when the particles counted are real and when they are false counts. Any real particle event shows up in all three detectors, while false counts will only be detected by one detector. Statistics are used to determine at which particle count levels the measured counts are considered to be real versus false. Other methods and apparatuses are disclosed.

A droplet generator includes a chamber including an enclosed space filled with gas having vapor, a tube extending through the chamber, a gas flow channel inside the tube, and a heater in the chamber. The tube includes a sidewall having an outer surface exposed to the enclosed space of the chamber, and an inner surface. The tube contains liquid. The heater is operable to change a phase of the liquid contained in the tube to vapor such that the vapor is provided into the enclosed space. A pressure in the enclosed space is higher than a pressure in the gas flow channel such that the vapor in the enclosed space flows to the gas flow channel by passing through the tube.

A device for detecting signal pulses in an analog measurement signal of a particle counter is disclosed. The device includes an AD converter and an evaluation unit, wherein the evaluation unit includes a slope evaluation unit, which determines signal pulses by evaluating the pulses between adjacent samples in the digital data stream of the AD converter in real time.