Flow monitored particle sensor

摘要

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.

主权项

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.