Flow sensors and flow sensing methods with extended linear range

摘要

One aspect of the invention provides a flow sensing apparatus including: a fluid channel that allows a fluid to flow in a first direction; a first temperature sensor arranged at a first position along the fluid channel; a second temperature sensor arranged at a second position along the fluid channel and separated from the first sensor by a predetermined distance along the fluid channel; a heating element arranged between the first and second thermoelectric sensors, the heating element being substantially equally spaced from the first and second thermoelectric sensors; a heating element temperature sensor for sensing a temperature of the heating element; and a control device configured to maintain the heating element at a substantially uniform temperature.

主权项

1. A method for determining a flow rate through a flow sensor including a conduit, a first temperature sensor positioned along the conduit, a second temperature sensor positioned along the conduit, a heating element positioned substantially equidistant between the first temperature sensor and the second temperature sensor along the conduit, and a heating element temperature sensor, the method comprising:
actuating the heating element; receiving temperature information from the first temperature sensor and the second temperature sensor at a zero flow rate; flowing a first known flow rate through the flow sensor to calculate a flow scalar value; flowing a second known flow rate through the flow sensor, the second known flow rate exceeding a maximum linear range flow rate of the flow sensor; receiving temperature information from the first temperature sensor, the second temperature sensor, and the heating element temperature sensor; computing a heating element compensation factor based on the temperature information received from the first temperature sensor, the second temperature sensor, and the heating element temperature sensor; flowing a fluid sample through the flow sensor; and calculating a flow rate based on a difference in temperatures between the first temperature sensor and the second temperature sensor, temperature information from the heating element temperature sensor, the flow scalar value, and the heating element compensation factor; thereby determining a flow rate through the flow sensor, wherein the flow rate is defined by (ΔT−ΔT0)(1+α(H0−H)) times the flow scalar value, wherein ΔT is a difference between the second temperature sensor and the first temperature sensor while the flow sensor is exposed to the first known flow rate, ΔT0 is a difference between the second temperature sensor and the first temperature sensor at the zero flow state, H0 is a temperature received from the heating element temperature sensor at the zero flow state by the heating element temperature sensor, H is a temperature received from the heating element at the non-zero flow state by the heating element temperature sensor, and α is a constant.