| 摘要 |
<p>PURPOSE:To detect the breaking of a wire a at a start without extending an input terminal on a control unit side by inputting a source voltage to a differential amplifier circuit with a signal that a bridge circuit sends when the voltage is below a lower-limit value. CONSTITUTION:In a normal state, the output voltage Vs of the bridge circuit 10 exceeds the reference voltage Vr of a comparator 14 at all times, the comparator 14 generates an H-level output to turn off a transistor (TR) 16 in a source voltage input circuit 17, and the output voltage of a flowmeter is nearly zero when the amount of liquid is zero. Here, if a hot film element 3 in the circuit 10 is broken, the output voltage Vs of the circuit 10 falls to zero, the output of the comparator 14 is inverted to an L level, and the TR 16 of the circuit 17 turns on. Consequently, the voltage Vs is inputted to the differential amplifier circuit 13 and its output is raised forcibly to the maximum-level voltage Vs. The breaking of a wire is therefore detected when the internal combustion engine is started.</p> |
