| 摘要 |
PURPOSE:To detect abnormality with a high precision to prevent the occurrence of secondary disaster such as a fire, by applying a test signal to an operational amplifier and by detecting the test signal from the feedback signal of a heat sensor to discriminate whether the circuit is normal or not. CONSTITUTION:When a test signal (c) is applied to an operational amplifier 1 within a range where a heat control system is not influenced badly, the amplifier 1 not only adds an instruction signal (a) and the test signal (c) but also subtracts a feedback signal (d), and the output is subjected to power amplification in 2 and is supplied to a heating body 4. A heat sensor 5 detects the heating value of the heating body 4 and outputs the feedback signal (d). Thus, the heat control system constitutes a closed loop to perform the heat control in accordance with the instruction signal (a). At this time, the feedback signal (d) includes the test signal (c), and a test signal detector 7 outputs an abnormality signal (e) when the test signal (c) is not detected. Consequently, it is discrimiated whether the heat control system is normal or not by this constitution, and thus, the abnormality of the circuit of the heat control system is detected with a high precision to prevent secondary disaster such as a fire surely. |
