Abstract: 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.

Abstract: 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.