| 摘要 |
<p>PURPOSE:To properly judge a failure mode which is peculiar to a flow sensor by diagnosing failure and state of the flow sensor in a composite-type flow meter. CONSTITUTION:When an output P1 changes from a preset initial value to a specified value according to secular change of upstream and downstream temperature-sensitive resistors 21 and 22 and fixed resistors 23 and 24 of a flow sensor 1 and an offset drift of a differential amplifier 25, a microcomputer 3 outputs an alarm A of failure. Also, when the microcomputer 3 receives a flow signal from a Karman flow meter 2 and when outputs P1 and P2 of the flow sensor 1 are equal to 0, the microcomputer 3 gives a warning for open- circuit failure of the upstream temperature-sensitive resistor 21. Also, when there is no flow signal from the Karman flow meter 2 and the output P1 of the flow sensor 1 exceeds and allowable value, for example 640 pulses, and the output P2 exceeds 1390 pulses, the microcomputer 3 issues a warning of open-circuited downstream temperature-sensitive resistor 22.</p> |
