Patent ID: 8408050

Claim:
A method for determining a fluid composition parameter of an unknown fluid using a flow sensor, wherein said flow sensor comprises a heater arranged between a first and a second temperature sensor, said method comprising the steps of contacting said unknown fluid to said first temperature sensor, then contacting said unknown fluid to said heater, and then contacting said unknown fluid to said second temperature sensor, measuring a first temperature, TP 1 , of the unknown fluid at the first temperature sensor, measuring a second temperature, TP 2 , of the unknown fluid at the second temperature sensor, determining a temperature difference, DTP, between TP 2 and TP 1 , and calculating a single temperature, T, wherein T =(k1 ×TP 1 ) +(k2 ×TP 2 ), with k1 ≠−k 2 , retrieving first calibration data, wherein said first calibration data was obtained from a calibration measurement carried out with a reference fluid of known composition, calculating, using said first calibration data, a reference temperature, Tref(DTP), equal to a single temperature of said reference fluid for said temperature difference DTP, and calculating a temperature offset, D, wherein D =T −Tref(DTP), and determining a value of the fluid composition parameter based upon the calculated value of D, wherein the step of determining the value of the fluid composition parameter comprises the step of referring to second calibration data which provides a corresponding value of the fluid composition parameter for the calculated value of the temperature offset D.