| 摘要 |
<p>PROBLEM TO BE SOLVED: To make the presence/absence of a fault in a flow velocity sensor detectable during flow velocity measurement by stopping the heating of a heater element and checking the output value of a sensor detecting circuit. SOLUTION: A flow velocity sensor 20 detects the heat transfer caused by a fluid moving on a heater element 4. When the inspection of the sensor 20 is requested, a sensor checking mechanism 50 stops the heating of the element 4 by turning on a switch. When the element 4 is cooled to the ambient temperature in the non-heating state of the element 4 after several milliseconds, the mechanism 50 reads the output value of a temperature amplifier circuit 40 and returns the element 4 to the original state by turning off the switch. When the element 4 is not heated, the output value of the circuit 40 indicates 0V, because no current difference occurs between temperature measuring resistance elements 5 and 6 irrespective of the presence/absence of the flow of the fluid. Therefore, the output of the sensor 20 can be discriminated as abnormal when the output value of the circuit 40 does not indicate 0V and normal when the output value indicates 0V.</p> |
