# US 9,518,913 B2 · Method for detecting particles in a fluid stream > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,518,913 B2 - Document ID: US9518913B2 - Status: Granted - Kind: B2 - Application number: 14/403,751 - Filed: 2013-06-20 - Published: 2015-05-07 - Granted: 2016-12-13 - Earliest claimed: 2012-07-03 - Assignees: Hydac Filter Systems GmbH - Applicants: Hydac Filter Systems GmbH - Inventors: Andreas Wilhelm - Web page: https://patentgrep.com/patent/US9518913B2 ## CPC - G01N 15/10: Investigating individual particles - G01N 15/1031: by measuring electrical or magnetic effects - G01N 2015/1026: {Recognising analyser failures, e.g. bubbles; Quality control for particle analysers} - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract A method for detecting particles in a fluid stream includes generating a measurement field that can be passed through by the fluid stream, acquiring and evaluating measurement values of the fluid stream passing through the measurement field, and detecting at least one particle by way of a distinctive sequence of measurement values. Each of the distinctive successions of measurement values is acquired and evaluated to determine if a particle or a gas bubble is passing through the measurement field. ## Claims ### Claim 1 A method for detecting particles in a fluid stream, comprising: generating a measurement field; passing the measuring field through the fluid stream; recording and evaluating measurement values in the fluid stream from the measurement field; detecting a particle by a characteristic sequence of the measurement values; recording and evaluating the characteristic sequence of the measurement values in terms of whether a particle or gas bubble is passing through the measurement field for an observation period greater than a measurement duration of a sequence of the measurement values characteristic of at least one particle or of at least one gas bubble; and determining whether a maximum of two or more extreme points have been counted once measurement values pass through the observation period. ### Claim 2 (depends on 1) A method according to claim 1 wherein the observation period is at least double the measurement duration. ### Claim 3 (depends on 1) A method according to claim 1 wherein the observation period is 3.5 times the measurement duration. ### Claim 4 (depends on 1) A method according to claim 1 wherein the sequence of the measurement values that is characteristic of a particle has a particle signal shape; and the sequence of the measurement values that is characteristic of a gas bubble has a gas bubble signal shape, the particle signal shape and the gas bubble signal shape being different. ### Claim 5 (depends on 4) A method according to claim 4 wherein the particle signal shape and the gas bubble signal shape at least partially coincide. ### Claim 6 (depends on 4) A method according to claim 4 wherein the particle signal shape has at least one extremum. ### Claim 7 (depends on 6) A method according to claim 6 wherein the particle signal shape has at least two extrema. ### Claim 8 (depends on 6) A method according to claim 6 wherein the particle signal shape follows a periodic curve. ### Claim 9 (depends on 8) A method according to claim 8 wherein the periodic curve is a sinusoidal curve. ### Claim 10 (depends on 6) A method according to claim 6 wherein each extremum is identified and evaluated by exceeding and subsequently dropping below at least one of an upper limit value or a lower limit value of recorded measurement values. ### Claim 11 (depends on 4) A method according to claim 4 wherein the gas bubble signal shape has at least three extrema. ### Claim 12 (depends on 11) A method according to claim 11 wherein the gas bubble signal shape has at least four extrema. ### Claim 13 (depends on 11) A method according to claim 11 wherein the gas bubble signal shape follows a periodic curve. ### Claim 14 (depends on 13) A method according to claim 13 wherein the periodic curve is a sinusoidal curve. ### Claim 15 (depends on 11) A method according to claim 11 wherein each extremum identified and evaluated by exceeding and subsequently dropping below at least one of an upper limit value or a lower limit value of recorded measurement values. ### Claim 16 (depends on 1) A method according to claim 1 wherein a noise of the measurement values is considered in evaluating such that only measurement values outside a predefined noise band between a lower noise value and an upper noise value are considered in the evaluating. ### Claim 17 (depends on 1) A method according to claim 1 wherein air bubbles are detected as gas bubbles.