Particle Measuring Systems, Inc.

Thomas A Bates

Matt Michaelis

Brett Haley

Cliff Ketcham

Gregg A Wagner

Ronald W Adkins

Paul B Hartigan

Richard A Alexander

Richard O Miller

Provided are particle analyzers and related methods for verifying calibration status of the particle analyzer, including independently of the presence or absence of particles. The method and analyzers include use of distinct and non-interfering time frequency domains: a middle frequency time domain and a low frequency time domain, and optionally a high frequency time domain. The high frequency time domain generates a laser facet drive current frequency modulation to prevent the laser facet from spatial-mode hopping. The middle frequency time domain is for particle detection. The low frequency time domain is for calibration status, including laser-pulse-light self-diagnostics, for the health or calibration status of the analyzer. By carefully selecting the frequency time domain ranges, there is non-interference, with the ability to self-diagnose the instrument that is particle-independent.

Calibration verification for optical particle analyzers

Provided are particle analyzers and related methods for verifying calibration status of the particle analyzer. The method includes the steps of providing an optical particle analyzer and modulating a power applied to a source of EMR. The method includes the steps of, in response to the modulating step, inducing a detector signal waveform and analyzing the detector signal waveform to determine a value of at least one diagnostic parameter associated with one or more of the source of EMR, an optical assembly, a chamber, a detector, and an optical collection system of the optical particle analyzer. The method includes the step of determining a calibration status of the optical particle analyzer based on the one or more determined values of the at least one diagnostic parameter.

Provided are systems and methods for accurate sensing of particle concentrations in fluids by employing a particle impactor system that allows for collection, growth and analysis of biological particles. The disclosed systems and methods make use of a pressure based flow sensor which permits the particle impactor system systems to accurately and reliably provide measurements of biological particle concentrations in the ambient environment. By incorporation of pressure sensors and pressure measurements into the flow measurement techniques, embodiments provide for the ability to use a particle impactor system to accurately measure environmental biological particle concentrations at a variety of atmospheric pressure conditions, such as at high altitude or with minimal perturbation from atmospheric weather conditions, without requiring recalibration or other adjustment of the sensors and control systems.

Pressure-based airflow sensing in particle impactor systems

Provided are devices and methods for monitoring flow rate in aerosol particle counters. The particle sensor has a particle counter, a flow measurement orifice comprising a differential pressure sensor for measuring differential pressure (DP) across the flow measurement orifice during particle sensor operation and a critical flow orifice. A vacuum source pulls ambient gas through each of the particle counter, flow measurement orifice and critical flow orifice. An atmospheric pressure sensor measures atmospheric pressure (AP) and a bench pressure sensor measures pressure in the particle sensor (BP). The output from the sensors is used to identify a flow condition, such as by a monitor operably connected to each of the differential pressure sensor, atmospheric pressure sensor and bench pressure sensor. In this manner, deviation in flow rate from a target flow rate is readily monitored without the need for expensive sensors or other flow-controlling components.

Flow monitored particle sensor

Described herein is a portable, low power consuming optical particle counter calibration verification system and reliable and sensitive methods for verifying the calibration status of a gas or liquid particle counter. The calibration verification systems described herein are useful for quickly determining the calibration status of an optical particle counter at its point of use, as well as for allowing the end user to determine if an optical particle counter is in need of a recalibration before the recommended calibration schedule suggests.

System and method for calibration verification of an optical particle counter

A particle sensor for optically detecting an unconstrained particle suspended in a flowing gas includes a sample chamber having a gas inlet and a gas outlet; a gas flow system for flowing said gas from said gas inlet through said sample chamber to said gas outlet, a source of light; an optical system directing said light through said sample chamber, an optical collection system located to collect light scattered by said particles in the gas, and a detection system located to detect the collected light. The total pressure drop through said gas flow system is 3 inches of water or less. The gas flow system includes an axial fan, which may be a high static pressure fan or a counter-rotating fan. In a 1.0 CFM system, the gas inlet nozzle has an area of 25 square millimeters or more.

Aerosol particle sensor with axial fan

A particle measurement system using a single component light collecting system with an aperture having a portion within direct view of the light detector. An aperture assembly extending into a sample may be self-concealing by having an extended portion to block light from directly illuminating the light detector. Alternatively, a smooth, reflective inside surface of the aperture assembly provides for self-concealment by causing spontaneous emitted light to have low angles of reflection. In either case, spontaneously emitted light is substantially prevented from reflecting directly into the light detector, thereby reducing light noise to the level of molecular noise.

Particle counter with self-concealing aperture assembly

A fluid particle counter comprising an inlet jet tip producing an air flow, a strip laser diode producing a laser beam, and a beam shaping system that includes an aspheric collimating lens, an achromatic spherical lens, a cylinder lens, and a series of cascading apertures. A retarder rotates the polarization so that the TE mode is along the direction of fluid flow. The optical system is designed so that along the flow axis the laser beam is single mode, while the multimodes due to the strip laser are constrained to the dimension perpendicular to the flow. The beam is pinched to a 35 micron waist and has a Gaussian profile along the flow direction which permits locating the beam within 3.5 mm of the flow tip while preventing stray light scattering from the tip. The beam profile along the axis perpendicular to the flow is closer to a square wave than a Gaussian. The particle counter output is substantially free of all noise except noise created by light scattered from molecules of the fluid, even for volumetric particle counters.

Particle counter with strip laser diode

The invention includes a particle sensor with a particle counter. A regenerative blower pulls ambient air into a flow within the particle counter, and a laser illuminates the flow to generate laser radiation indicative of particles within the flow. A detector detects the laser radiation; and particle sensing electronics counts particles within the flow at a preselected volumetric flow rate, e.g., 1 CFM. Preferably, the particle counter includes a plurality of pressure sensors; and a blower speed voltage controller adjusts the speed of the blower according to signals from the pressure sensors to achieve the preselected volumetric flow rate. The regenerative blower permits use of a high efficiency exhaust filter to filter air exhausted from the blower. An airflow path between the particle counter and the regenerative blower preferably has at least one bend between the particle counter and the blower to increase compactness of the system. An aerosol manifold can be connected for fluid communication with an inlet of the particle counter such that the regenerative blower draws air from the manifold at the preselected volumetric flow rate. The manifold samples ambient atmospheric air at a second CFM rate, e.g., 3 CFM, that is greater than the preselected volumetric flow rate. A turbomolecular pump can replace the regenerative blower for high pressure differential particle sensing environments.

Growing community of inventors

Boulder, CO, United States of America

Thomas A Bates