Flow monitored particle sensor
First Claim
1. A method of monitoring flow rate of a gas in a particle sensor, said method comprising the steps of:
- providing a particle sensor comprising;
a flow measurement orifice comprising a differential pressure sensor for measuring differential pressure across said flow measurement orifice;
a critical orifice;
a vacuum system for generating gas flow across said flow measurement orifice and said critical orifice;
generating a flow of gas through said particle sensor by establishing a vacuum pressure at a position downstream of said critical orifice;
determining a pressure drop (DPI) across said flow measurement orifice;
determining atmospheric pressure (API);
determining a pressure in said particle sensor (BPI) at a position that is upstream of said critical orifice;
identifying a flow condition from said DPI, API and BPI values, wherein said flow condition is a flow rate error condition; and
identifying said flow rate error condition as a vacuum-induced flow loss or an inlet-induced flow loss;
thereby monitoring said flow rate in said particle sensor.
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Accused Products
Abstract
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.
97 Citations
23 Claims
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1. A method of monitoring flow rate of a gas in a particle sensor, said method comprising the steps of:
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providing a particle sensor comprising; a flow measurement orifice comprising a differential pressure sensor for measuring differential pressure across said flow measurement orifice; a critical orifice; a vacuum system for generating gas flow across said flow measurement orifice and said critical orifice; generating a flow of gas through said particle sensor by establishing a vacuum pressure at a position downstream of said critical orifice; determining a pressure drop (DPI) across said flow measurement orifice; determining atmospheric pressure (API); determining a pressure in said particle sensor (BPI) at a position that is upstream of said critical orifice; identifying a flow condition from said DPI, API and BPI values, wherein said flow condition is a flow rate error condition; and identifying said flow rate error condition as a vacuum-induced flow loss or an inlet-induced flow loss; thereby monitoring said flow rate in said particle sensor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of monitoring volumetric flow rate of a gas in a particle sensor, said method comprising the steps of:
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providing a particle sensor comprising; a flow measurement orifice comprising a differential pressure sensor for measuring differential pressure across said flow measurement orifice, a critical orifice; a vacuum system for generating gas flow across said flow measurement orifice and said critical orifice; generating a flow of gas through said particle sensor by establishing a vacuum pressure at a position downstream of said critical orifice; determining a pressure drop (DPI) across said flow measurement orifice; determining atmospheric pressure (API); and determining a pressure in said particle sensor (BPI) at a position that is upstream of said critical orifice; and identifying a flow condition from said DP, AP and BP values, wherein said flow condition is identified as; a vacuum-induced flow loss for;
DPIcorr<
(1−
TOLERANCE)2*DPItarget;
or
DPIcorr>
(1+TOLERANCE)2*DPItarget;
wherein;DPIcorr is the differential pressure sensor current reading across said flow measurement orifice during particle sensor operation; TOLERANCE is a user-selected flow rate tolerance level; DPItarget is a differential pressure sensor target value calculated as;
DPCcorr*(BPIcorr/BPCcor), wherein;DPCcorr is the differential pressure sensor value during system calibration; BPIcorr is the bench pressure value during particle sensor operation; and BPCcorr is the bench pressure value during system calibration; or; an inlet-induced flow loss for;
APRinsitu<
(1−
TOLERANCE)*APRcalibration;
or
APRinsitu>
(1+TOLERANCE)*APRcalibration;
wherein;APRinsitu is the pressure ratio of APIcorr and BPIcorr during particle sensor operation;
(BPIcorr/APIcorr);APIcorr is the atmospheric pressure value during particle sensor operation; BPIcorr is the bench pressure value during particle sensor operation; TOLERANCE is a user-selected flow rate tolerance level; APRcalibration is the pressure ratio of APCcorr and BPCcorr;
(BPCcorr/APCcorr), wherein;BPCcorr is the bench pressure value at calibration; and APCcorr is the atmospheric pressure at calibration; thereby monitoring said volumetric flow rate in said particle sensor.
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16. A particle sensor comprising:
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a particle counter; a flow measurement orifice comprising a differential pressure sensor for measuring differential pressure across said flow measurement orifice (DPI) during particle sensor operation; a critical flow orifice; a vacuum source for pulling ambient gas through each of said particle counter, flow measurement orifice and critical flow orifice; an atmospheric pressure sensor for measuring atmospheric pressure (API); a bench pressure sensor for measuring pressure in said particle sensor (BPI); a monitor operably connected to each of said differential pressure sensor, atmospheric pressure sensor and bench pressure sensor, wherein said monitor identifies a flow rate error from said DPI, API and BPI, wherein said flow rate error is identified as a vacuum-induced flow loss or an inlet-induced flow loss. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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23. A particle sensor comprising:
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a particle counter; a flow measurement orifice comprising a differential pressure sensor for measuring differential pressure across said flow measurement orifice (DPI) during particle sensor operation; a critical flow orifice; a vacuum source for pulling ambient gas through each of said particle counter, flow measurement orifice and critical flow orifice; an atmospheric pressure sensor for measuring atmospheric pressure (API); a bench pressure sensor for measuring pressure in said particle sensor (BPI); a monitor operably connected to each of said differential pressure sensor, atmospheric pressure sensor and bench pressure sensor, wherein said monitor identifies a flow condition from said DPI, API and BPI, and said flow condition is a flow rate error for one or more of;
DPIcorr<
(1−
TOLERANCE)2*DPItarget;
DPIcorr>
(1+TOLERANCE)2*DPItarget;
APRinsitu<
(1−
TOLERANCE)*APRcalibration; and
APRinsitu>
(1+TOLERANCE)*APRcalibration;
wherein;DPIcorr is the differential pressure sensor current reading across said flow measurement orifice during particle sensor operation; TOLERANCE is a user-selected flow rate tolerance level; DPItarget is a differential pressure sensor target value calculated as;
DPCcorr*(BPIcorr/BPCcor), wherein;DPCcorr is the differential pressure sensor value during system calibration; BPIcorr is the bench pressure value during particle sensor operation; and BPCcorr is the bench pressure value during system calibration; APRinsitu is the pressure ratio of APIcorr and BPIcorr during particle sensor operation;
(BPIcorr/APIcorr), wherein;APIcorr is the atmospheric pressure value during particle sensor operation; BPIcorr is the bench pressure value during particle sensor operation; APRcalibration is the pressure ratio of APCcorr and BPCcorr;
(BPCcorr/APCcorr), wherein;APCcorr is the atmospheric pressure at calibration.
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Specification