METHOD FOR FORMING LEAK DETECTING SIGNAL WHEN LEAKAGE FROM BOILER TUBE IS DETECTED

摘要

PURPOSE:To detect leakage from a boiler tube regardless of the state of load fluctuation by detecting the minimum amplitude value of acoustic vibration for every specified period of a boiler, and forming a leakage detecting signal from the minimum amplitude value. CONSTITUTION:A minimum holding circuit 72 sequentially receives amplitude values which are held with a peak holding circuit 71. The minimum amplitude value which is the smallest within the specified period determined by the circuit constant is sequentially outputted with the elapse of time. That is, the difference between a reference voltage which is supplied from a constant voltage circuit 73 and the inputted amplitude value undergoes peak holding in a capacitor 721 in the circuit 72. The minimum amplitude value which is the smallest at every specified period is sequentially outputted through an output terminal OUT. At this time, the reference voltage which is supplied from the circuit 73 is set so that the voltage is larger than all amplitude values which are held in the circuit 71. In this way, a leak detecting signal is formed from the minimum amplitude value which is sequentially outputted from the circuit 71.