| 摘要 |
PROBLEM TO BE SOLVED: To provide a gain history apparatus capable of analyzing a gain history by storing the gain histories and narrowing parts at which anomalies have occurred on the basis of results of analysis. SOLUTION: A transmitting circuit 12 controls either one of acoustic transducers TD1 and TD2 and intermittently transmits ultrasonic signals into a gas channel. A receiving circuit 13 receives the transmitted ultrasonic signals. An amplifier 13a amplifies the received ultrasonic signals. A CPU in aμCOM 14 adjusts the gain of the amplifier 13a so that the received ultrasonic signals may be maintained at a certain level. The CPU in aμCOM 14 records an adjustment history of the gain of the amplifier 13a. COPYRIGHT: (C)2005,JPO&NCIPI
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