Patent ID: 6453739
Filing Date: 2002-09-24
Classification: G01F

Abstract:
A control system for a hot element air flow sensor of the type having a resistive heating element with an input end and an output end, said control system comprising:means for generating a first fixed frequency pulse train through the heating element, said first pulse train having a first predetermined voltage amplitude at the input end of the heating element, means for generating a second fixed frequency pulse train through the heating element, said second pulse train having a first predetermined voltage amplitude at the input end of the heating element, said second pulse train having the same frequency as said first pulse train but mutually independent of said first pulse train, means for determining an output voltage amplitude of said second pulse train at the output end of the heating element, and means for varying the duty cycle of said first pulse train to maintain said output voltage amplitude at a second predetermined voltage level, whereby the duty cycle of said first pulse train is proportional to the air flow rate through the air flow sensor.