| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a heating resistor air flowmeter capable of obtaining a highly accurate ratiometric function with simple structure. SOLUTION: Using a comparator 8 in which a delta wave shape frequency function voltage Vw output from a frequency function generating circuit 7 is supplied to one input, a voltage Vei output from a differential amplifier 9 is supplied to the other input so as to obtain a PWM signal with a pulse width determined by a signal V0 representing an air flow rate. From a pulse output circuit 10 controlled by the PWM signal, a signal equal to an internal reference voltage VINT with a pulse width determined by the signal V0 and a wave height value supplied from an internal reference power supply circuit 5 is obtained and fed back to the differential amplifier 9. Thus a time ratio D of the PWM signal output from the comparator 8 is established as following relationship. D=VO/VINT.</p> |
