DETERMINATION OF FLUID COMPOSITION IN A MASS FLOW CONTROLLER

摘要

A method for determining a fluid composition parameter, e.g., a fluid identifier, a mixing ratio or a parameter describing heat transfer properties, of an unknown fluid in a mass flow controller is disclosed. A control valve of the mass flow controller is set so as to establish a constant flow, preferably zero flow, through the mass flow controller. A heating element of the flow sensor is heated, and at least one temperature value is measured with temperature sensors arranged on both sides of the heater while the fluid contacts the flow sensor. First calibration data (LUT1) are retrieved. The first calibration data have, as input values, temperature values measured with the flow sensor at the previously established constant flow and have, as output values, values of the fluid composition parameter. The first calibration data are used to determine the fluid composition parameter from the measured temperature value.

主权项

1. A method for determining a fluid composition parameter of an unknown fluid in a mass flow controller, the mass flow controller comprising a flow sensor and a control valve, the flow sensor comprising a heating element arranged between a first and a second temperature sensor, the method comprising:
(a) actuating the control valve to establish a constant flow through the mass flow controller; (b) activating the heating element of the flow sensor and measuring at least one temperature value with the first and/or second temperature sensors of the flow sensor while the fluid contacts the flow sensor; (c) retrieving first calibration data, the first calibration data having, as input values, temperature values measured with the flow sensor at said constant flow and having, as output values, values of said fluid composition parameter; and (d) using said first calibration data to determine said fluid composition parameter from the measured temperature value.