US 8,800,383 B2 · Flow monitored particle sensor

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.

Claims23

Dependent claims

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.

9 more elements

A method of monitoring volumetric 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);
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.

36 more elements

A particle sensor comprising:

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.

4 more elements

Dependencies are inferred from the claim text.

Flow monitored particle sensor

Life of this patent

Flow monitored particle sensor

Life of this patent

Abstract

Claims23