Method for measuring a fluid composition parameter by means of a flow sensor
AssigneeSensirion AG
InventorsFelix Mayer, Mark Hornung, Samuel Wehrli
Life of this patent
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Abstract
The flow of a fluid of unknown composition is measured by leading the fluid over a first temperature sensor, a heater and a second temperature sensor. The temperature difference DTP between the temperature sensors is measured, as well as the temperature T of at least one of them. In addition, calibration data is used to store the temperature Tref of a known reference fluid. The offset T−Tref at a given temperature difference DTP is a direct measure of the composition of the fluid and allows to retrieve any parameter depending on the same.
Claims11
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, TP1, of the unknown fluid at the first temperature sensor,
- measuring a second temperature, TP2, of the unknown fluid at the second temperature sensor,
- determining a temperature difference, DTP, between TP2 and TP1, and calculating a single temperature, T, wherein T =(k1 ×TP1) +(k2 ×TP2), with k1 ≠−k2,
- 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.
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, TPI, of the unknown fluid at the first temperature sensor,
- measuring a second temperature, TP2, of the unknown fluid at the second temperature sensor,
- determining a temperature difference, DTP, between TP2 and TP1, and calculating a single temperature, T, wherein T =(k1 ×TP1) +(k2 ×TP2), with k1 ≠−k2,
- 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 said parameter comprises calculating the parameter as a function of said temperature offset D and a fluid temperature TF.
Dependencies are inferred from the claim text.