| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a thermal air flowmeter capable of determining the existence/absence of liquid adhesion of moisture, an oil content or the like to a sensor chip. <P>SOLUTION: Liquid adhesion determining means 22a compares a first signal outputted from a heater temperature control part 20 in accordance with temperature change of a heating heater 12 with a second signal outputted from a flow rate detecting part 21 in accordance with temperature change of a resistance temperature sensor 13 to determine whether a liquid body is adhered to a sensor chip. The first signal is voltage obtained from current caused to flow to the heating heater 12, and the voltage is converted into a digital value and inputted to a digital operation part 22. The second signal is a potential difference between two middle point terminals 30a and 30b of a bridge circuit 30, and the potential difference is converted into a digital value and inputted to the digital operation part 22. The digital operation part 22 determines that a liquid body is adhered to the sensor chip when the first signal indicates voltage that is equal to or more than the maximum air flow rate and when the second signal indicates voltage in a zero state of an air flow rate. <P>COPYRIGHT: (C)2013,JPO&INPIT |
