Systems and methods for reducing false positive particle detection events in a particle detector

Patent metadata

Field	Value
Publication number	US-12461010-B2
Application number	US-202418947333-A
Country	US
Kind code	B2
Filing date	Nov 14, 2024
Priority date	Nov 16, 2023
Publication date	Nov 4, 2025
Grant date	Nov 4, 2025

Abstract

A method for reducing false-positive particle detection events of an optical particle detection system includes: filtering raw particle count data to produce filtered particle count data. The filtering includes: temporarily storing the raw particle count data for a buffering time period; segmenting the raw particle count data into a series of elemental data intervals; examining each elemental data interval for a noise signature; identifying a noise signature in the segmented raw particle count data; in response to the identified noise signature, flagging one or more sequential elemental data intervals as corresponding to a noise event; and removing the one or more flagged elemental data intervals from the raw particle count data to produce the filtered particle count data, and/or generating replacement data and substituting the replacement data for the one or more flagged elemental data intervals to produce the filtered particle count data.

First claim

We claim:

1 . A method for reducing false-positive particle detection events of an optical particle detector, the method comprising:
flowing a particle-containing fluid through a detection region; exposing the fluid in the detection region to a beam of electromagnetic radiation, wherein interaction between particles of the particle-containing fluid and the beam of electromagnetic radiation generates scattered or emitted electromagnetic radiation from the particles; directing at least a portion of the scattered or emitted electromagnetic radiation from the particles onto a photodetector; generating raw particle count data via the photodetector, wherein the raw particle count data includes a plurality of channels, each channel being correlated to a different particle size bin; filtering the raw particle count data to produce filtered particle count data, wherein the filtering comprises:
temporarily storing the raw particle count data for a buffering time period;
segmenting the raw particle count data into a series of elemental data intervals;
examining each elemental data interval for a noise signature;
identifying a noise signature in the segmented raw particle count data;
in response to the identified noise signature, flagging one or more sequential elemental data intervals as corresponding to a noise event; and
removing the one or more flagged elemental data intervals from the raw particle count data to produce the filtered particle count data, and/or generating replacement data and substituting the replacement data for the one or more flagged elemental data intervals to produce the filtered particle count data;
periodically reporting a particle measurement output to a user at a reporting interval, wherein the particle measurement output is based on the filtered particle count data; and wherein the reporting interval has a greater time duration than that of the elemental data intervals.

2 . The method of claim 1 , wherein generating the replacement data comprises calculating historical average data to produce the replacement data or interpolating the raw particle count data from a beginning point of the noise event to an end point of the noise event to produce the replacement data.

3 . The method of claim 1 , wherein identifying the detector noise signature comprises:
receiving data from a first channel of the raw particle count data, the first channel being correlated to a first particle size bin; receiving data from a second channel of the raw particle count data, the second channel being correlated to a second particle size bin; calculating, for a first elemental data interval, a first unfiltered particle count for particles of the first size bin; calculating, for the first elemental data interval, a second unfiltered particle count for particles of the second size bin; determining a ratio of the second unfiltered particle count to the first unfiltered particle count; and if the ratio falls below a threshold value, then identifying the data of the first and second channel as having the detector noise signature.

4 . The method of claim 3 , comprising:
calculating, for a data interval comprising at least the first elemental data interval and a second elemental data interval, a third unfiltered particle count for particles of a third size bin; determining a ratio of the third unfiltered particle count to the first unfiltered particle count; and if the ratio falls below a ratio threshold value, then identifying the data of the first and second channel as having the detector noise signature.

5 . The method of claim 1 , wherein examining each elemental data interval comprises:
when a raw particle count of a first elemental data interval falls below a first particle count threshold value, and a raw particle count of the next sequential elemental data interval in the series exceeds the first particle count threshold value, beginning a data evaluation period; continuing the data evaluation period for so long as each consecutive raw particle count of the series of sequential elemental data intervals exceeds the respective particle count threshold value; and when a raw particle count of the series falls below the first particle count threshold value, ending the data evaluation period; summing the raw particle counts from the first channel over the data evaluation period; summing the raw particle counts from the second channel over the data evaluation period; if the sum of the first channel raw particle counts exceeds a summed particle count threshold value, then calculating a ratio of the sum of the second channel raw particle counts to the sum of the first channel raw particle counts; if the ratio falls below a noise ratio threshold value, then identifying all the particle counts of the data evaluation period as having the detector noise signature.

6 . The method of claim 1 , wherein a first channel is correlated to a first particle size bin and a second channel is correlated to a second particle size bin;
summing the raw particle counts from the first channel for a first predetermined number of sequential elemental data intervals; summing the raw particle counts from the second channel for the first predetermined number of sequential elemental data intervals; calculating a first ratio of the sum of the second channel raw particle counts for the first predetermined number of sequential elemental data intervals to the sum of the first channel raw particle counts for the first predetermined number of sequential elemental data intervals; wherein if the first ratio falls below a noise ratio threshold value, then identifying all the particle counts of the first predetermined number of sequential elemental data intervals as having the detector noise signature.

7 . The method of claim 1 wherein identifying the detector noise signature comprises:
for a first time interval comprising one or more elemental data intervals:
(a) comparing a raw particle count of a first channel of the plurality of channels to a predetermined first channel threshold value, wherein the first channel threshold value is such that at or above the first channel threshold value, at least one particle would be statistically likely to have been detected in a second channel of the plurality of channels, the second channel corresponding to particles of a larger size bin than the first channel;
(b) if the raw particle count of the first channel exceeds the first channel threshold value, then calculating a ratio of the raw particle count of the first channel to a raw particle count of the second channel and comparing the calculated ratio to a ratio threshold value;
(c) if the calculated ratio exceeds the ratio threshold value, then identifying the data of the first time interval as having the detector noise signature and removing it from the raw particle count data of the first interval to produce filtered first interval data; and

repeating steps (a)-(c) for a second time interval, wherein the second time interval is longer in duration than the first time interval and subsumes the first interval, and wherein the data of the second time interval includes the filtered first interval data.

8 . The method of claim 1 , comprising:
producing the beam of electromagnetic radiation via a laser; monitoring an operating parameter of the laser; comparing the laser operating parameter to a laser threshold value; and if the operating parameter exceeds the laser threshold value, then identifying any raw particle count data associated with the rate of change as having the detector noise signature.

9 . The method of claim 1 , comprising:
producing the beam of electromagnetic radiation via a laser; monitoring an electrical

Assignees

• Particle Measuring Syst

Inventors

• Cilke Joseph Thomas
• Haley Brett
• Maclaughlin Scott
• Knollenberg Brian A
• Martinez Benjamin
• Ellinwood Clayton

Classifications

• G01N2015/1486

  Counting the particles · CPC title

• G01N2015/1402

  Data analysis by thresholding or gating operations performed on the acquired signals or stored data · CPC title

• G01N2015/0038

  Investigating nanoparticles · CPC title

• G01N2015/0046

  in gas, e.g. smoke · CPC title

• G01N2015/0053

  in liquids, e.g. trouble · CPC title